# 3991

## 3,991 is an odd composite number composed of two prime numbers multiplied together.

What does the number 3991 look like?

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

3991 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 3991:

### 13 × 307

See below for interesting mathematical facts about the number 3991 from the Numbermatics database.

### Names of 3991

• Cardinal: 3991 can be written as Three thousand, nine hundred ninety-one.

### Scientific notation

• Scientific notation: 3.991 × 103

### Factors of 3991

• Number of distinct prime factors ω(n): 2
• Total number of prime factors Ω(n): 2
• Sum of prime factors: 320

### Divisors of 3991

• Number of divisors d(n): 4
• Complete list of divisors:
• Sum of all divisors σ(n): 4312
• Sum of proper divisors (its aliquot sum) s(n): 321
• 3991 is a deficient number, because the sum of its proper divisors (321) is less than itself. Its deficiency is 3670

### Bases of 3991

• Binary: 1111100101112
• Base-36: 32V

### Squares and roots of 3991

• 3991 squared (39912) is 15928081
• 3991 cubed (39913) is 63568971271
• The square root of 3991 is 63.1743618885
• The cube root of 3991 is 15.8620960711

### Scales and comparisons

How big is 3991?
• 3,991 seconds is equal to 1 hour, 6 minutes, 31 seconds.
• To count from 1 to 3,991 would take you about six minutes.

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 3991 cubic inches would be around 1.3 feet tall.

### Recreational maths with 3991

• 3991 backwards is 1993
• The number of decimal digits it has is: 4
• The sum of 3991's digits is 22
• More coming soon!