21087808 has 56 divisors (see below), whose sum is σ = 48394112. Its totient is φ = 8930304.

The previous prime is 21087779. The next prime is 21087809. The reversal of 21087808 is 80878012.

It is a tau number, because it is divible by the number of its divisors (56).

It is not an unprimeable number, because it can be changed into a prime (21087809) 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, 45916 + ... + 46372.

Almost surely, 2^21087808 is an apocalyptic number.

21087808 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21087808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24197056).

21087808 is an abundant number, since it is smaller than the sum of its proper divisors (27306304).

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

21087808 is a wasteful number, since it uses less digits than its factorization.

21087808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 579 (or 569 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 34.

The square root of 21087808 is about 4592.1463391316. The cubic root of 21087808 is about 276.2764156473.

The spelling of 21087808 in words is "twenty-one million, eighty-seven thousand, eight hundred eight".