21312265 has 8 divisors (see below), whose sum is σ = 27542088. Its totient is φ = 15738240.

The previous prime is 21312257. The next prime is 21312289. The reversal of 21312265 is 56221312.

It can be written as a sum of positive squares in 4 ways, for example, as 299209 + 21013056 = 547^2 + 4584^2 .

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

It is not a de Polignac number, because 21312265 - 2³ = 21312257 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 163876 + ... + 164005.

It is an arithmetic number, because the mean of its divisors is an integer number (3442761).

Almost surely, 2^21312265 is an apocalyptic number.

It is an amenable number.

21312265 is a deficient number, since it is larger than the sum of its proper divisors (6229823).

21312265 is a wasteful number, since it uses less digits than its factorization.

21312265 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 327899.

The product of its digits is 720, while the sum is 22.

The square root of 21312265 is about 4616.5208761577. The cubic root of 21312265 is about 277.2531798782.

Adding to 21312265 its reverse (56221312), we get a palindrome (77533577).

The spelling of 21312265 in words is "twenty-one million, three hundred twelve thousand, two hundred sixty-five".