21503808 has 84 divisors (see below), whose sum is σ = 63365380. Its totient is φ = 6967296.

The previous prime is 21503791. The next prime is 21503821. The reversal of 21503808 is 80830512.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 13483584 + 8020224 = 3672^2 + 2832^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 20808 + ... + 21816.

Almost surely, 2^21503808 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21503808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31682690).

21503808 is an abundant number, since it is smaller than the sum of its proper divisors (41861572).

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

21503808 is a wasteful number, since it uses less digits than its factorization.

21503808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1064 (or 1051 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21503808 is about 4637.2198567676. The cubic root of 21503808 is about 278.0813039631.

The spelling of 21503808 in words is "twenty-one million, five hundred three thousand, eight hundred eight".