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27991 = 231217
BaseRepresentation
bin110110101010111
31102101201
412311113
51343431
6333331
7144415
oct66527
942351
1027991
111a037
1214247
13c982
14a2b5
158461
hex6d57

27991 has 4 divisors (see below), whose sum is σ = 29232. Its totient is φ = 26752.

The previous prime is 27983. The next prime is 27997. The reversal of 27991 is 19972.

27991 is nontrivially palindromic in base 5.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 27991 - 23 = 27983 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 6 and base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (27997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 586 + ... + 631.

It is an arithmetic number, because the mean of its divisors is an integer number (7308).

227991 is an apocalyptic number.

27991 is a deficient number, since it is larger than the sum of its proper divisors (1241).

27991 is a wasteful number, since it uses less digits than its factorization.

27991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1240.

The product of its digits is 1134, while the sum is 28.

The square root of 27991 is about 167.3051105017. The cubic root of 27991 is about 30.3626358819.

The spelling of 27991 in words is "twenty-seven thousand, nine hundred ninety-one".

Divisors: 1 23 1217 27991