21572645 has 4 divisors (see below), whose sum is σ = 25887180. Its totient is φ = 17258112.

The previous prime is 21572641. The next prime is 21572653. The reversal of 21572645 is 54627512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2927521 + 18645124 = 1711^2 + 4318^2 .

It is a cyclic number.

It is not a de Polignac number, because 21572645 - 2² = 21572641 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21572641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2157260 + ... + 2157269.

It is an arithmetic number, because the mean of its divisors is an integer number (6471795).

Almost surely, 2^21572645 is an apocalyptic number.

It is an amenable number.

21572645 is a deficient number, since it is larger than the sum of its proper divisors (4314535).

21572645 is an equidigital number, since it uses as much as digits as its factorization.

21572645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4314534.

The product of its digits is 16800, while the sum is 32.

The square root of 21572645 is about 4644.6361536723. The cubic root of 21572645 is about 278.3777149239.

The spelling of 21572645 in words is "twenty-one million, five hundred seventy-two thousand, six hundred forty-five".