21390824 has 32 divisors (see below), whose sum is σ = 49365120. Its totient is φ = 8462016.

The previous prime is 21390797. The next prime is 21390833. The reversal of 21390824 is 42809312.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13964 + ... + 15419.

It is an arithmetic number, because the mean of its divisors is an integer number (1542660).

Almost surely, 2^21390824 is an apocalyptic number.

It is an amenable number.

21390824 is an abundant number, since it is smaller than the sum of its proper divisors (27974296).

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

21390824 is a wasteful number, since it uses less digits than its factorization.

21390824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29409 (or 29405 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 21390824 is about 4625.0215134635. The cubic root of 21390824 is about 277.5934225396.

The spelling of 21390824 in words is "twenty-one million, three hundred ninety thousand, eight hundred twenty-four".