21036556 has 12 divisors (see below), whose sum is σ = 37318792. Its totient is φ = 10374048.

The previous prime is 21036539. The next prime is 21036563. The reversal of 21036556 is 65563012.

It is a super-2 number, since 2×21036556² = 885073376682272, which contains 22 as substring.

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 35730 + ... + 36313.

Almost surely, 2^21036556 is an apocalyptic number.

It is an amenable number.

21036556 is a deficient number, since it is larger than the sum of its proper divisors (16282236).

21036556 is a wasteful number, since it uses less digits than its factorization.

21036556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72120 (or 72118 counting only the distinct ones).

The product of its (nonzero) digits is 5400, while the sum is 28.

The square root of 21036556 is about 4586.5625472678. The cubic root of 21036556 is about 276.0524125065.

Adding to 21036556 its reverse (65563012), we get a palindrome (86599568).

The spelling of 21036556 in words is "twenty-one million, thirty-six thousand, five hundred fifty-six".