21904824 has 64 divisors (see below), whose sum is σ = 56881440. Its totient is φ = 7024640.

The previous prime is 21904807. The next prime is 21904837. The reversal of 21904824 is 42840912.

It is a junction number, because it is equal to n+sod(n) for n = 21904791 and 21904800.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 111094 + ... + 111290.

Almost surely, 2^21904824 is an apocalyptic number.

21904824 is a gapful number since it is divisible by the number (24) 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 21904824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28440720).

21904824 is an abundant number, since it is smaller than the sum of its proper divisors (34976616).

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

21904824 is a wasteful number, since it uses less digits than its factorization.

21904824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 360 (or 356 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 21904824 is about 4680.2589671940. The cubic root of 21904824 is about 279.7992779125.

The spelling of 21904824 in words is "twenty-one million, nine hundred four thousand, eight hundred twenty-four".