21320617 has 4 divisors (see below), whose sum is σ = 21348496. Its totient is φ = 21292740.

The previous prime is 21320581. The next prime is 21320639. The reversal of 21320617 is 71602312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21320617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21320317) 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, 12759 + ... + 14332.

It is an arithmetic number, because the mean of its divisors is an integer number (5337124).

Almost surely, 2^21320617 is an apocalyptic number.

It is an amenable number.

21320617 is a deficient number, since it is larger than the sum of its proper divisors (27879).

21320617 is an equidigital number, since it uses as much as digits as its factorization.

21320617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27878.

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21320617 is about 4617.4253648543. The cubic root of 21320617 is about 277.2893924556.

Adding to 21320617 its reverse (71602312), we get a palindrome (92922929).

The spelling of 21320617 in words is "twenty-one million, three hundred twenty thousand, six hundred seventeen".