21132556 has 6 divisors (see below), whose sum is σ = 36981980. Its totient is φ = 10566276.

The previous prime is 21132509. The next prime is 21132557. The reversal of 21132556 is 65523112.

It is a self number, because there is not a number n which added to its sum of digits gives 21132556.

It is not an unprimeable number, because it can be changed into a prime (21132557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2641566 + ... + 2641573.

Almost surely, 2^21132556 is an apocalyptic number.

It is an amenable number.

21132556 is a deficient number, since it is larger than the sum of its proper divisors (15849424).

21132556 is a wasteful number, since it uses less digits than its factorization.

21132556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5283143 (or 5283141 counting only the distinct ones).

The product of its digits is 1800, while the sum is 25.

The square root of 21132556 is about 4597.0159886605. The cubic root of 21132556 is about 276.4716956683.

Adding to 21132556 its reverse (65523112), we get a palindrome (86655668).

The spelling of 21132556 in words is "twenty-one million, one hundred thirty-two thousand, five hundred fifty-six".