21791457 has 32 divisors (see below), whose sum is σ = 33390720. Its totient is φ = 14040000.

The previous prime is 21791353. The next prime is 21791477. The reversal of 21791457 is 75419712.

It is a happy number.

It is not a de Polignac number, because 21791457 - 2²⁰ = 20742881 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21791477) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 166282 + ... + 166412.

It is an arithmetic number, because the mean of its divisors is an integer number (1043460).

Almost surely, 2^21791457 is an apocalyptic number.

21791457 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21791457 is a deficient number, since it is larger than the sum of its proper divisors (11599263).

21791457 is a wasteful number, since it uses less digits than its factorization.

21791457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 302 (or 296 counting only the distinct ones).

The product of its digits is 17640, while the sum is 36.

The square root of 21791457 is about 4668.1320675405. The cubic root of 21791457 is about 279.3157484362.

The spelling of 21791457 in words is "twenty-one million, seven hundred ninety-one thousand, four hundred fifty-seven".