21317577 has 4 divisors (see below), whose sum is σ = 28423440. Its totient is φ = 14211716.

The previous prime is 21317539. The next prime is 21317623. The reversal of 21317577 is 77571312.

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 not a de Polignac number, because 21317577 - 2¹⁰ = 21316553 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21317377) 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, 3552927 + ... + 3552932.

It is an arithmetic number, because the mean of its divisors is an integer number (7105860).

Almost surely, 2^21317577 is an apocalyptic number.

It is an amenable number.

21317577 is a deficient number, since it is larger than the sum of its proper divisors (7105863).

21317577 is an equidigital number, since it uses as much as digits as its factorization.

21317577 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7105862.

The product of its digits is 10290, while the sum is 33.

The square root of 21317577 is about 4617.0961653403. The cubic root of 21317577 is about 277.2762127273.

Adding to 21317577 its reverse (77571312), we get a palindrome (98888889).

The spelling of 21317577 in words is "twenty-one million, three hundred seventeen thousand, five hundred seventy-seven".