# 1991

## 1,991 is an odd composite number composed of two prime numbers multiplied together.

What does the number 1991 look like?

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

1991 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 1991:

### 11 × 181

See below for interesting mathematical facts about the number 1991 from the Numbermatics database.

### Names of 1991

• Cardinal: 1991 can be written as One thousand, nine hundred ninety-one.

### Scientific notation

• Scientific notation: 1.991 × 103

### Factors of 1991

• Number of distinct prime factors ω(n): 2
• Total number of prime factors Ω(n): 2
• Sum of prime factors: 192

### Divisors of 1991

• Number of divisors d(n): 4
• Complete list of divisors:
• Sum of all divisors σ(n): 2184
• Sum of proper divisors (its aliquot sum) s(n): 193
• 1991 is a deficient number, because the sum of its proper divisors (193) is less than itself. Its deficiency is 1798

### Bases of 1991

• Binary: 111110001112
• Base-36: 1JB

### Squares and roots of 1991

• 1991 squared (19912) is 3964081
• 1991 cubed (19913) is 7892485271
• The square root of 1991 is 44.6206230347
• The cube root of 1991 is 12.5802832639

### Scales and comparisons

How big is 1991?
• 1,991 seconds is equal to 33 minutes, 11 seconds.
• To count from 1 to 1,991 would take you about thirty-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 1991 cubic inches would be around 1 feet tall.

### Recreational maths with 1991

• 1991 is the same when its digits are reversed! That makes it a palindromic number.
• The number of decimal digits it has is: 4
• The sum of 1991's digits is 20
• More coming soon!