21553836 has 24 divisors (see below), whose sum is σ = 51463104. Its totient is φ = 7017360.

The previous prime is 21553789. The next prime is 21553837. The reversal of 21553836 is 63835512.

It is a junction number, because it is equal to n+sod(n) for n = 21553797 and 21553806.

It is not an unprimeable number, because it can be changed into a prime (21553837) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 20370 + ... + 21401.

It is an arithmetic number, because the mean of its divisors is an integer number (2144296).

Almost surely, 2^21553836 is an apocalyptic number.

It is an amenable number.

21553836 is an abundant number, since it is smaller than the sum of its proper divisors (29909268).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21553836 is a wasteful number, since it uses less digits than its factorization.

21553836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41821 (or 41819 counting only the distinct ones).

The product of its digits is 21600, while the sum is 33.

The square root of 21553836 is about 4642.6109033603. The cubic root of 21553836 is about 278.2967863695.

The spelling of 21553836 in words is "twenty-one million, five hundred fifty-three thousand, eight hundred thirty-six".