21565628 has 24 divisors (see below), whose sum is σ = 45007872. Its totient is φ = 8840304.

The previous prime is 21565601. The next prime is 21565633. The reversal of 21565628 is 82656512.

It is a super-2 number, since 2×21565628² = 930152622068768, which contains 22 as substring.

It is a congruent number.

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, 16100 + ... + 17387.

It is an arithmetic number, because the mean of its divisors is an integer number (1875328).

Almost surely, 2^21565628 is an apocalyptic number.

21565628 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21565628 is an abundant number, since it is smaller than the sum of its proper divisors (23442244).

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

21565628 is a wasteful number, since it uses less digits than its factorization.

21565628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33521 (or 33519 counting only the distinct ones).

The product of its digits is 28800, while the sum is 35.

The square root of 21565628 is about 4643.8807047555. The cubic root of 21565628 is about 278.3475287281.

The spelling of 21565628 in words is "twenty-one million, five hundred sixty-five thousand, six hundred twenty-eight".