21556131 has 8 divisors (see below), whose sum is σ = 28857024. Its totient is φ = 14313000.

The previous prime is 21556103. The next prime is 21556141. The reversal of 21556131 is 13165512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-21556131 is a prime.

It is a super-2 number, since 2×21556131² = 929333567378322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21556141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13561 + ... + 15066.

It is an arithmetic number, because the mean of its divisors is an integer number (3607128).

Almost surely, 2^21556131 is an apocalyptic number.

21556131 is a deficient number, since it is larger than the sum of its proper divisors (7300893).

21556131 is a wasteful number, since it uses less digits than its factorization.

21556131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28881.

The product of its digits is 900, while the sum is 24.

The square root of 21556131 is about 4642.8580637362. The cubic root of 21556131 is about 278.3066634738.

The spelling of 21556131 in words is "twenty-one million, five hundred fifty-six thousand, one hundred thirty-one".