# 15991

## 15,991 is a prime number. Like all primes greater than two, it is odd and has no factors apart from itself and one.

What does the number 15991 look like?

As a prime, it is not composed of any other numbers and has no internal structure.

15991 is a prime number. Like all primes (except two), it is an odd number.

## Prime factorization of 15991:

### 15991

See below for interesting mathematical facts about the number 15991 from the Numbermatics database.

### Names of 15991

• Cardinal: 15991 can be written as Fifteen thousand, nine hundred ninety-one.

### Scientific notation

• Scientific notation: 1.5991 × 104

### Factors of 15991

• Number of distinct prime factors ω(n): 1
• Total number of prime factors Ω(n): 1
• Sum of prime factors: 15991

### Divisors of 15991

• Number of divisors d(n): 2
• Complete list of divisors:
• Sum of all divisors σ(n): 15992
• Sum of proper divisors (its aliquot sum) s(n): 1
• 15991 is a deficient number, because the sum of its proper divisors (1) is less than itself. Its deficiency is 15990

### Bases of 15991

• Binary: 111110011101112
• Base-36: CC7

### Squares and roots of 15991

• 15991 squared (159912) is 255712081
• 15991 cubed (159913) is 4089091887271
• The square root of 15991 is 126.4555257789
• The cube root of 15991 is 25.1936954079

### Scales and comparisons

How big is 15991?
• 15,991 seconds is equal to 4 hours, 26 minutes, 31 seconds.
• To count from 1 to 15,991 would take you about four hours.

This is a very rough estimate, based on a speaking rate of half a second every third order of magnitude. If you speak quickly, you could probably say any randomly-chosen number between one and a thousand in around half a second. Very big numbers obviously take longer to say, so we add half a second for every extra x1000. (We do not count involuntary pauses, bathroom breaks or the necessity of sleep in our calculation!)

• A cube with a volume of 15991 cubic inches would be around 2.1 feet tall.

### Recreational maths with 15991

• 15991 backwards is 19951
• The number of decimal digits it has is: 5
• The sum of 15991's digits is 25
• More coming soon!