21633720 has 32 divisors (see below), whose sum is σ = 64901520. Its totient is φ = 5768960.

The previous prime is 21633719. The next prime is 21633743. The reversal of 21633720 is 2733612.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 90021 + ... + 90260.

Almost surely, 2^21633720 is an apocalyptic number.

21633720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21633720 is an abundant number, since it is smaller than the sum of its proper divisors (43267800).

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

21633720 is a wasteful number, since it uses less digits than its factorization.

21633720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180295 (or 180291 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 24.

The square root of 21633720 is about 4651.2062951454. The cubic root of 21633720 is about 278.6401753877.

The spelling of 21633720 in words is "twenty-one million, six hundred thirty-three thousand, seven hundred twenty".