21561628 has 24 divisors (see below), whose sum is σ = 41690880. Its totient is φ = 9675120.

The previous prime is 21561607. The next prime is 21561629. The reversal of 21561628 is 82616512.

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21561628.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561629) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 375 + ... + 6577.

It is an arithmetic number, because the mean of its divisors is an integer number (1737120).

Almost surely, 2^21561628 is an apocalyptic number.

It is an amenable number.

21561628 is a deficient number, since it is larger than the sum of its proper divisors (20129252).

21561628 is a wasteful number, since it uses less digits than its factorization.

21561628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6297 (or 6295 counting only the distinct ones).

The product of its digits is 5760, while the sum is 31.

The square root of 21561628 is about 4643.4500104987. The cubic root of 21561628 is about 278.3303183326.

The spelling of 21561628 in words is "twenty-one million, five hundred sixty-one thousand, six hundred twenty-eight".