21056531 has 4 divisors (see below), whose sum is σ = 21198000. Its totient is φ = 20915064.

The previous prime is 21056527. The next prime is 21056537. The reversal of 21056531 is 13565012.

21056531 = T₅₅ + T₅₆ + ... + T₅₀₁.

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 21056531 - 2² = 21056527 is a prime.

It is a super-2 number, since 2×21056531² = 886754995507922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21056497 and 21056506.

It is not an unprimeable number, because it can be changed into a prime (21056537) 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, 70511 + ... + 70808.

It is an arithmetic number, because the mean of its divisors is an integer number (5299500).

Almost surely, 2^21056531 is an apocalyptic number.

21056531 is a deficient number, since it is larger than the sum of its proper divisors (141469).

21056531 is a wasteful number, since it uses less digits than its factorization.

21056531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141468.

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 21056531 is about 4588.7395872941. The cubic root of 21056531 is about 276.1397589106.

The spelling of 21056531 in words is "twenty-one million, fifty-six thousand, five hundred thirty-one".