Number Checkers

Predicate functions to check/compare numbers. These functions return true or false.

isPrime

Determines whether a given number is a prime number using an efficient 6k ± 1 optimization.

Function Signature

isPrime(number: number): boolean;

Parameters

• number — The integer to evaluate for prime number check.

Returns

• true if the number is a prime, otherwise false.

Examples

Notes

• Uses a fast prime number check based on:
  • Simple divisibility rules for 2 and 3.
  • 6k ± 1 optimization to reduce unnecessary checks.
• Returns false for all numbers below 2.
• Ideal for performance on small to moderate integers.

isEven

Checks if a number is even (divisible by 2).

Function Signature

isEven(input: Numeric): boolean;

Parameters

• input: The number or numeric string to check.

Returns

Returns true if the number is even, otherwise false.

Notes

• Handles both number and numeric string inputs.
• Returns false for non-numeric strings and non-finite numbers or NaN.

Example

isOdd

Checks if a number is odd (not divisible by 2).

Function Signature

isOdd(input: Numeric): boolean;

Parameters

• input: The number or numeric string to check.

Returns

Returns true if the number is odd, otherwise false.

Notes

• Handles both number and numeric string inputs.
• Returns false for non-numeric strings and non-finite numbers or NaN.

Example

isMultiple

Checks if a number is a multiple of another number.

Function Signature

isMultiple(input: number, multipleOf: number): boolean;

Parameters

• input: The number to check.
• multipleOf: The potential multiple.

Returns

Returns true if input is a multiple of multipleOf, otherwise false.

Example

Notes

• Returns true when input is 0 and multipleOf is 0 (mathematically undefined case)
• Handles negative numbers correctly

isPerfectSquare

Checks if a number is a perfect square.

Function Signature

isPerfectSquare(num: number): boolean;

Parameters

• num: The number to check.

Returns

Returns true if the number is a perfect square, otherwise false.

Example

isFibonacci

Checks if a number is part of the Fibonacci sequence.

Function Signature

isFibonacci(num: number): boolean;

Parameters

• num: The number to check.

Returns

Returns true if the number is in the Fibonacci sequence, otherwise false.

Example

Algorithm

Uses the mathematical property that a number n is Fibonacci if and only if one or both of (5*n^2 + 4) or (5*n^2 - 4) is a perfect square.

areInvalidNumbers

Checks if any input is not a finite number.

Function Signature

areInvalidNumbers(...numbers: number[]): boolean;

Parameters

• numbers: Spread of numbers to validate.

Returns

Returns true if any input is not finite (NaN, Infinity, etc.), otherwise false.

Example

Common Use Cases

• Validating user input
• Sanity checking before mathematical operations
• Data quality verification

Notes

• Returns true for:
  • NaN
  • Infinity
  • -Infinity
  • Non-number values
• Returns false for all finite numbers including zero

Aliases