# 391

## 391 is an odd composite number composed of two prime numbers multiplied together.

What does the number 391 look like?

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

391 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 391:

### 17 × 23

See below for interesting mathematical facts about the number 391 from the Numbermatics database.

### Names of 391

• Cardinal: 391 can be written as Three hundred ninety-one.

### Scientific notation

• Scientific notation: 3.91 × 102

### Factors of 391

• Number of distinct prime factors ω(n): 2
• Total number of prime factors Ω(n): 2
• Sum of prime factors: 40

### Divisors of 391

• Number of divisors d(n): 4
• Complete list of divisors:
• Sum of all divisors σ(n): 432
• Sum of proper divisors (its aliquot sum) s(n): 41
• 391 is a deficient number, because the sum of its proper divisors (41) is less than itself. Its deficiency is 350

### Bases of 391

• Binary: 1100001112
• Base-36: AV

### Squares and roots of 391

• 391 squared (3912) is 152881
• 391 cubed (3913) is 59776471
• The square root of 391 is 19.7737199333
• The cube root of 391 is 7.3123828115

### Scales and comparisons

How big is 391?
• 391 seconds is equal to 6 minutes, 31 seconds.
• To count from 1 to 391 would take you about three 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 391 cubic inches would be around 0.6 feet tall.

### Recreational maths with 391

• 391 backwards is 193
• The number of decimal digits it has is: 3
• The sum of 391's digits is 13
• More coming soon!