21566736 has 105 divisors (see below), whose sum is σ = 64140519. Its totient is φ = 7021728.

The previous prime is 21566719. The next prime is 21566737. The reversal of 21566736 is 63766512.

The square root of 21566736 is 4644.

It is a perfect power (a square), and thus also a powerful number.

21566736 is a `hidden beast` number, since 21 + 566 + 73 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

Its product of digits (45360) is a multiple of the sum of its prime divisors (48).

It is a self number, because there is not a number n which added to its sum of digits gives 21566736.

It is not an unprimeable number, because it can be changed into a prime (21566737) by changing a digit.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 501531 + ... + 501573.

Almost surely, 2^21566736 is an apocalyptic number.

21566736 is the 4644-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21566736

21566736 is an abundant number, since it is smaller than the sum of its proper divisors (42573783).

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

21566736 is an frugal number, since it uses more digits than its factorization.

21566736 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112 (or 48 counting only the distinct ones).

The product of its digits is 45360, while the sum is 36.

The cubic root of 21566736 is about 278.3522956312.

Multiplying 21566736 by its sum of digits (36), we get a square (776402496 = 27864²).

21566736 divided by its sum of digits (36) gives a square (599076 = 774²).

The spelling of 21566736 in words is "twenty-one million, five hundred sixty-six thousand, seven hundred thirty-six".