21317265 has 24 divisors (see below), whose sum is σ = 37059048. Its totient is φ = 11335680.

The previous prime is 21317249. The next prime is 21317267. The reversal of 21317265 is 56271312.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 5919489 + 15397776 = 2433^2 + 3924^2 .

It is not a de Polignac number, because 21317265 - 2⁴ = 21317249 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21317267) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 25555 + ... + 26375.

It is an arithmetic number, because the mean of its divisors is an integer number (1544127).

Almost surely, 2^21317265 is an apocalyptic number.

It is an amenable number.

21317265 is a deficient number, since it is larger than the sum of its proper divisors (15741783).

21317265 is a wasteful number, since it uses less digits than its factorization.

21317265 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1409 (or 1406 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 21317265 is about 4617.0623777463. The cubic root of 21317265 is about 277.2748600000.

Adding to 21317265 its reverse (56271312), we get a palindrome (77588577).

The spelling of 21317265 in words is "twenty-one million, three hundred seventeen thousand, two hundred sixty-five".