21642653 has 4 divisors (see below), whose sum is σ = 22781760. Its totient is φ = 20503548.

The previous prime is 21642637. The next prime is 21642667. The reversal of 21642653 is 35624612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21642653 - 2⁴ = 21642637 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21642553) 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, 569525 + ... + 569562.

It is an arithmetic number, because the mean of its divisors is an integer number (5695440).

Almost surely, 2^21642653 is an apocalyptic number.

It is an amenable number.

21642653 is a deficient number, since it is larger than the sum of its proper divisors (1139107).

21642653 is a wasteful number, since it uses less digits than its factorization.

21642653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1139106.

The product of its digits is 8640, while the sum is 29.

The square root of 21642653 is about 4652.1664845532. The cubic root of 21642653 is about 278.6785221625.

The spelling of 21642653 in words is "twenty-one million, six hundred forty-two thousand, six hundred fifty-three".