21156457 has 16 divisors (see below), whose sum is σ = 25315200. Its totient is φ = 17297280.

The previous prime is 21156419. The next prime is 21156463. The reversal of 21156457 is 75465112.

It is not a de Polignac number, because 21156457 - 2¹⁵ = 21123689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21156407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17482 + ... + 18652.

It is an arithmetic number, because the mean of its divisors is an integer number (1582200).

Almost surely, 2^21156457 is an apocalyptic number.

It is an amenable number.

21156457 is a deficient number, since it is larger than the sum of its proper divisors (4158743).

21156457 is a wasteful number, since it uses less digits than its factorization.

21156457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1296.

The product of its digits is 8400, while the sum is 31.

The square root of 21156457 is about 4599.6148751825. The cubic root of 21156457 is about 276.5758865726.

The spelling of 21156457 in words is "twenty-one million, one hundred fifty-six thousand, four hundred fifty-seven".