21255697 has 4 divisors (see below), whose sum is σ = 21273840. Its totient is φ = 21237556.

The previous prime is 21255679. The next prime is 21255721. The reversal of 21255697 is 79655212.

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 21255697 - 2⁷ = 21255569 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21255607) 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, 7183 + ... + 9700.

It is an arithmetic number, because the mean of its divisors is an integer number (5318460).

Almost surely, 2^21255697 is an apocalyptic number.

It is an amenable number.

21255697 is a deficient number, since it is larger than the sum of its proper divisors (18143).

21255697 is a wasteful number, since it uses less digits than its factorization.

21255697 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18142.

The product of its digits is 37800, while the sum is 37.

The square root of 21255697 is about 4610.3901136455. The cubic root of 21255697 is about 277.0076631226.

It can be divided in two parts, 21255 and 697, that added together give a cube (21952 = 28³).

The spelling of 21255697 in words is "twenty-one million, two hundred fifty-five thousand, six hundred ninety-seven".