21056523 has 32 divisors (see below), whose sum is σ = 32140800. Its totient is φ = 12182016.

The previous prime is 21056507. The next prime is 21056527. The reversal of 21056523 is 32565012.

It is not a de Polignac number, because 21056523 - 2⁴ = 21056507 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21056493 and 21056502.

It is not an unprimeable number, because it can be changed into a prime (21056527) 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, 33708 + ... + 34326.

It is an arithmetic number, because the mean of its divisors is an integer number (1004400).

Almost surely, 2^21056523 is an apocalyptic number.

21056523 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21056523 is a deficient number, since it is larger than the sum of its proper divisors (11084277).

21056523 is a wasteful number, since it uses less digits than its factorization.

21056523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 691.

The product of its (nonzero) digits is 1800, while the sum is 24.

The square root of 21056523 is about 4588.7387155950. The cubic root of 21056523 is about 276.1397239393.

The spelling of 21056523 in words is "twenty-one million, fifty-six thousand, five hundred twenty-three".