21255365 has 4 divisors (see below), whose sum is σ = 25506444. Its totient is φ = 17004288.

The previous prime is 21255361. The next prime is 21255383. The reversal of 21255365 is 56355212.

It is a happy number.

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 5841889 + 15413476 = 2417^2 + 3926^2 .

It is a cyclic number.

It is not a de Polignac number, because 21255365 - 2² = 21255361 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 (21255361) 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, 2125532 + ... + 2125541.

It is an arithmetic number, because the mean of its divisors is an integer number (6376611).

Almost surely, 2^21255365 is an apocalyptic number.

It is an amenable number.

21255365 is a deficient number, since it is larger than the sum of its proper divisors (4251079).

21255365 is an equidigital number, since it uses as much as digits as its factorization.

21255365 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4251078.

The product of its digits is 9000, while the sum is 29.

The square root of 21255365 is about 4610.3541078750. The cubic root of 21255365 is about 277.0062208893.

The spelling of 21255365 in words is "twenty-one million, two hundred fifty-five thousand, three hundred sixty-five".