21651572 has 12 divisors (see below), whose sum is σ = 38266116. Its totient is φ = 10718400.

The previous prime is 21651563. The next prime is 21651587. The reversal of 21651572 is 27515612.

It can be written as a sum of positive squares in 2 ways, for example, as 16434916 + 5216656 = 4054^2 + 2284^2 .

It is a hoax number, since the sum of its digits (29) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26393 + ... + 27200.

It is an arithmetic number, because the mean of its divisors is an integer number (3188843).

Almost surely, 2^21651572 is an apocalyptic number.

It is an amenable number.

21651572 is a deficient number, since it is larger than the sum of its proper divisors (16614544).

21651572 is a wasteful number, since it uses less digits than its factorization.

21651572 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53698 (or 53696 counting only the distinct ones).

The product of its digits is 4200, while the sum is 29.

The square root of 21651572 is about 4653.1249714574. The cubic root of 21651572 is about 278.7167983138.

The spelling of 21651572 in words is "twenty-one million, six hundred fifty-one thousand, five hundred seventy-two".