21064440 has 64 divisors (see below), whose sum is σ = 65383200. Its totient is φ = 5422592.

The previous prime is 21064363. The next prime is 21064471. The reversal of 21064440 is 4446012.

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, 454 + ... + 6506.

Almost surely, 2^21064440 is an apocalyptic number.

21064440 is a gapful number since it is divisible by the number (20) 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 21064440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32691600).

21064440 is an abundant number, since it is smaller than the sum of its proper divisors (44318760).

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

21064440 is a wasteful number, since it uses less digits than its factorization.

21064440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6096 (or 6092 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 21.

The square root of 21064440 is about 4589.6012898726. The cubic root of 21064440 is about 276.1743280104.

The spelling of 21064440 in words is "twenty-one million, sixty-four thousand, four hundred forty".