21255893 has 4 divisors (see below), whose sum is σ = 21398700. Its totient is φ = 21113088.

The previous prime is 21255859. The next prime is 21255919. The reversal of 21255893 is 39855212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1203409 + 20052484 = 1097^2 + 4478^2 .

It is a cyclic number.

It is not a de Polignac number, because 21255893 - 2²² = 17061589 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 (21255823) 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, 71180 + ... + 71477.

It is an arithmetic number, because the mean of its divisors is an integer number (5349675).

Almost surely, 2^21255893 is an apocalyptic number.

It is an amenable number.

21255893 is a deficient number, since it is larger than the sum of its proper divisors (142807).

21255893 is a wasteful number, since it uses less digits than its factorization.

21255893 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142806.

The product of its digits is 21600, while the sum is 35.

The square root of 21255893 is about 4610.4113699322. The cubic root of 21255893 is about 277.0085145545.

The spelling of 21255893 in words is "twenty-one million, two hundred fifty-five thousand, eight hundred ninety-three".