# 18991

## 18,991 is an odd composite number composed of two prime numbers multiplied together.

What does the number 18991 look like?

This visualization shows the relationship between its 2 prime factors (large circles) and 4 divisors.

18991 is an odd composite number. It is composed of two distinct prime numbers multiplied together. It has a total of four divisors.

## Prime factorization of 18991:

### 7 × 2713

See below for interesting mathematical facts about the number 18991 from the Numbermatics database.

### Names of 18991

• Cardinal: 18991 can be written as Eighteen thousand, nine hundred ninety-one.

### Scientific notation

• Scientific notation: 1.8991 × 104

### Factors of 18991

• Number of distinct prime factors ω(n): 2
• Total number of prime factors Ω(n): 2
• Sum of prime factors: 2720

### Divisors of 18991

• Number of divisors d(n): 4
• Complete list of divisors:
• Sum of all divisors σ(n): 21712
• Sum of proper divisors (its aliquot sum) s(n): 2721
• 18991 is a deficient number, because the sum of its proper divisors (2721) is less than itself. Its deficiency is 16270

### Bases of 18991

• Binary: 1001010001011112
• Base-36: ENJ

### Squares and roots of 18991

• 18991 squared (189912) is 360658081
• 18991 cubed (189913) is 6849257616271
• The square root of 18991 is 137.8078372227
• The cube root of 18991 is 26.6798025561

### Scales and comparisons

How big is 18991?
• 18,991 seconds is equal to 5 hours, 16 minutes, 31 seconds.
• To count from 1 to 18,991 would take you about five 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 18991 cubic inches would be around 2.2 feet tall.

### Recreational maths with 18991

• 18991 backwards is 19981
• The number of decimal digits it has is: 5
• The sum of 18991's digits is 28
• More coming soon!