27991531 has 4 divisors (see below), whose sum is σ = 28007064. Its totient is φ = 27976000.

The previous prime is 27991519. The next prime is 27991549. The reversal of 27991531 is 13519972.

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 27991531 - 2¹¹ = 27989483 is a prime.

It is a super-2 number, since 2×27991531² = 1567051615447922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (27991511) 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, 4645 + ... + 8806.

It is an arithmetic number, because the mean of its divisors is an integer number (7001766).

Almost surely, 2^27991531 is an apocalyptic number.

27991531 is a deficient number, since it is larger than the sum of its proper divisors (15533).

27991531 is a wasteful number, since it uses less digits than its factorization.

27991531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15532.

The product of its digits is 17010, while the sum is 37.

The square root of 27991531 is about 5290.7023163281. The cubic root of 27991531 is about 303.6282787766.

The spelling of 27991531 in words is "twenty-seven million, nine hundred ninety-one thousand, five hundred thirty-one".