21643902 has 32 divisors (see below), whose sum is σ = 54969600. Its totient is φ = 6183864.

The previous prime is 21643891. The next prime is 21643913. The reversal of 21643902 is 20934612.

It is an interprime number because it is at equal distance from previous prime (21643891) and next prime (21643913).

It is a Harshad number since it is a multiple of its sum of digits (27).

21643902 is a modest number, since divided by 43902 gives 216 as remainder.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28252 + ... + 29007.

It is an arithmetic number, because the mean of its divisors is an integer number (1717800).

Almost surely, 2^21643902 is an apocalyptic number.

21643902 is an abundant number, since it is smaller than the sum of its proper divisors (33325698).

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

21643902 is a wasteful number, since it uses less digits than its factorization.

21643902 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57277 (or 57271 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 21643902 is about 4652.3007211486. The cubic root of 21643902 is about 278.6838829159.

The spelling of 21643902 in words is "twenty-one million, six hundred forty-three thousand, nine hundred two".