21265855 has 16 divisors (see below), whose sum is σ = 28070784. Its totient is φ = 15367680.

The previous prime is 21265847. The next prime is 21265859. The reversal of 21265855 is 55856212.

It is not a de Polignac number, because 21265855 - 2³ = 21265847 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 21265855.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21265859) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 426 + ... + 6535.

It is an arithmetic number, because the mean of its divisors is an integer number (1754424).

Almost surely, 2^21265855 is an apocalyptic number.

21265855 is a deficient number, since it is larger than the sum of its proper divisors (6804929).

21265855 is a wasteful number, since it uses less digits than its factorization.

21265855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7026.

The product of its digits is 24000, while the sum is 34.

The square root of 21265855 is about 4611.4916241928. The cubic root of 21265855 is about 277.0517829919.

The spelling of 21265855 in words is "twenty-one million, two hundred sixty-five thousand, eight hundred fifty-five".