Unusual Number Calculator

Input a number check if the number is an Unusual Number or generate all Unusual Numbers within a specified range by providing a start and end value.

Unusual Number Check or Generate

What is an Unusual Number?

An Unusual Number is a natural number with a unique factor property: its largest prime factor is greater than its square root. For example: The number 20 is an Unusual Number because its largest prime factor, 5, is greater than \( \sqrt{20} \approx 4.47 \).

All prime numbers are Unusual Numbers because their largest prime factor is the number itself, which is always greater than their square root.

How to Determine an Unusual Number

To check if a number is an Unusual Number or generate all Unusual Numbers within a range, follow these steps:

  1. Perform prime factorization: Break the number into its prime factors and identify the largest one.
  2. Calculate the square root: Find the square root of the given number.
  3. Check the prime factor condition: If the largest prime factor is greater than the square root, the number is an Unusual Number; otherwise, it is not.

Examples

Example 1: Is 30 an Unusual Number?

Solution:

1. Prime factorization:

\( 30 = 2 \times 3 \times 5 \), largest prime factor = 5.

2. Calculate the square root:

\(\sqrt{30} \approx 5.48\)

3. Check the prime factor condition:

\(5 \lt 5.48\)

Result: 30 is not an Unusual Number.

Example 2: Is 102 an Unusual Number?

Solution:

1. Prime factorization:

\( 102 = 2 \times 3 \times 17 \), largest prime factor = 17.

2. Calculate the square root:

\(\sqrt{102} \approx 10.0995\)

3. Check the prime factor condition:

\(17 \gt 10.0995\)

Result: 102 is an Unusual Number.

First 100 Unusual Numbers

  • 2
  • 3
  • 5
  • 6
  • 7
  • 10
  • 11
  • 13
  • 14
  • 15
  • 17
  • 19
  • 20
  • 21
  • 22
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  • 26
  • 28
  • 29
  • 31
  • 33
  • 34
  • 35
  • 37
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  • 41
  • 42
  • 43
  • 44
  • 46
  • 47
  • 51
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  • 55
  • 57
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  • 61
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  • 65
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  • 71
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  • 82
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  • 86
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  • 91
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  • 93
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  • 95
  • 97
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  • 101
  • 102
  • 103
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