21653904 has 40 divisors (see below), whose sum is σ = 57308832. Its totient is φ = 7041280.

The previous prime is 21653899. The next prime is 21653909. The reversal of 21653904 is 40935612.

It is an interprime number because it is at equal distance from previous prime (21653899) and next prime (21653909).

It is not an unprimeable number, because it can be changed into a prime (21653909) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3534 + ... + 7469.

Almost surely, 2^21653904 is an apocalyptic number.

21653904 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21653904 is an abundant number, since it is smaller than the sum of its proper divisors (35654928).

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

21653904 is a wasteful number, since it uses less digits than its factorization.

21653904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11055 (or 11049 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 30.

The square root of 21653904 is about 4653.3755489967. The cubic root of 21653904 is about 278.7268044270.

The spelling of 21653904 in words is "twenty-one million, six hundred fifty-three thousand, nine hundred four".