21293621 has 4 divisors (see below), whose sum is σ = 21980544. Its totient is φ = 20606700.

The previous prime is 21293599. The next prime is 21293633. The reversal of 21293621 is 12639212.

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 21293621 - 2¹⁸ = 21031477 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21293521) 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, 343415 + ... + 343476.

It is an arithmetic number, because the mean of its divisors is an integer number (5495136).

Almost surely, 2^21293621 is an apocalyptic number.

It is an amenable number.

21293621 is a deficient number, since it is larger than the sum of its proper divisors (686923).

21293621 is an equidigital number, since it uses as much as digits as its factorization.

21293621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 686922.

The product of its digits is 1296, while the sum is 26.

The square root of 21293621 is about 4614.5011648064. The cubic root of 21293621 is about 277.1723091318.

The spelling of 21293621 in words is "twenty-one million, two hundred ninety-three thousand, six hundred twenty-one".