21265921 has 8 divisors (see below), whose sum is σ = 22932000. Its totient is φ = 19654560.

The previous prime is 21265913. The next prime is 21265943. The reversal of 21265921 is 12956212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21265921 - 2³ = 21265913 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21265921.

It is not an unprimeable number, because it can be changed into a prime (21269921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12871 + ... + 14428.

It is an arithmetic number, because the mean of its divisors is an integer number (2866500).

Almost surely, 2^21265921 is an apocalyptic number.

It is an amenable number.

21265921 is a deficient number, since it is larger than the sum of its proper divisors (1666079).

21265921 is a wasteful number, since it uses less digits than its factorization.

21265921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27359.

The product of its digits is 2160, while the sum is 28.

The square root of 21265921 is about 4611.4987802232. The cubic root of 21265921 is about 277.0520696078.

The spelling of 21265921 in words is "twenty-one million, two hundred sixty-five thousand, nine hundred twenty-one".