21553636 has 24 divisors (see below), whose sum is σ = 41489280. Its totient is φ = 9735072.

The previous prime is 21553633. The next prime is 21553643. The reversal of 21553636 is 63635512.

It is a junction number, because it is equal to n+sod(n) for n = 21553598 and 21553607.

It is not an unprimeable number, because it can be changed into a prime (21553633) 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, 1966 + ... + 6853.

It is an arithmetic number, because the mean of its divisors is an integer number (1728720).

Almost surely, 2^21553636 is an apocalyptic number.

21553636 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21553636 is a deficient number, since it is larger than the sum of its proper divisors (19935644).

21553636 is a wasteful number, since it uses less digits than its factorization.

21553636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8883 (or 8881 counting only the distinct ones).

The product of its digits is 16200, while the sum is 31.

The square root of 21553636 is about 4642.5893637064. The cubic root of 21553636 is about 278.2959255865.

The spelling of 21553636 in words is "twenty-one million, five hundred fifty-three thousand, six hundred thirty-six".