21285408 has 24 divisors (see below), whose sum is σ = 55874448. Its totient is φ = 7095104.

The previous prime is 21285367. The next prime is 21285409. The reversal of 21285408 is 80458212.

It is a tau number, because it is divible by the number of its divisors (24).

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21285409) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110766 + ... + 110957.

It is an arithmetic number, because the mean of its divisors is an integer number (2328102).

Almost surely, 2^21285408 is an apocalyptic number.

It is an amenable number.

21285408 is an abundant number, since it is smaller than the sum of its proper divisors (34589040).

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

21285408 is a wasteful number, since it uses less digits than its factorization.

21285408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221736 (or 221728 counting only the distinct ones).

The product of its (nonzero) digits is 5120, while the sum is 30.

The square root of 21285408 is about 4613.6111669711. The cubic root of 21285408 is about 277.1366692108.

The spelling of 21285408 in words is "twenty-one million, two hundred eighty-five thousand, four hundred eight".