21317165 has 4 divisors (see below), whose sum is σ = 25580604. Its totient is φ = 17053728.

The previous prime is 21317147. The next prime is 21317209. The reversal of 21317165 is 56171312.

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 9572836 + 11744329 = 3094^2 + 3427^2 .

It is a cyclic number.

It is not a de Polignac number, because 21317165 - 2²⁴ = 4539949 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2131712 + ... + 2131721.

It is an arithmetic number, because the mean of its divisors is an integer number (6395151).

Almost surely, 2^21317165 is an apocalyptic number.

It is an amenable number.

21317165 is a deficient number, since it is larger than the sum of its proper divisors (4263439).

21317165 is an equidigital number, since it uses as much as digits as its factorization.

21317165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4263438.

The product of its digits is 1260, while the sum is 26.

The square root of 21317165 is about 4617.0515483369. The cubic root of 21317165 is about 277.2744264308.

Adding to 21317165 its reverse (56171312), we get a palindrome (77488477).

The spelling of 21317165 in words is "twenty-one million, three hundred seventeen thousand, one hundred sixty-five".