21745808 has 30 divisors (see below), whose sum is σ = 49013046. Its totient is φ = 9319296.

The previous prime is 21745799. The next prime is 21745901. The reversal of 21745808 is 80854712.

It can be written as a sum of positive squares in only one way, i.e., 21086464 + 659344 = 4592^2 + 812^2 .

It is a hoax number, since the sum of its digits (35) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 13085 + ... + 14652.

Almost surely, 2^21745808 is an apocalyptic number.

21745808 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21745808 is an abundant number, since it is smaller than the sum of its proper divisors (27267238).

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

21745808 is a wasteful number, since it uses less digits than its factorization.

21745808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27759 (or 27746 counting only the distinct ones).

The product of its (nonzero) digits is 17920, while the sum is 35.

The square root of 21745808 is about 4663.2400753124. The cubic root of 21745808 is about 279.1205741184.

The spelling of 21745808 in words is "twenty-one million, seven hundred forty-five thousand, eight hundred eight".