21317517 has 12 divisors (see below), whose sum is σ = 33160764. Its totient is φ = 13118400.

The previous prime is 21317509. The next prime is 21317521. The reversal of 21317517 is 71571312.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 7322436 + 13995081 = 2706^2 + 3741^2 .

It is not a de Polignac number, because 21317517 - 2³ = 21317509 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21317017) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 90984 + ... + 91217.

It is an arithmetic number, because the mean of its divisors is an integer number (2763397).

Almost surely, 2^21317517 is an apocalyptic number.

It is an amenable number.

21317517 is a deficient number, since it is larger than the sum of its proper divisors (11843247).

21317517 is a wasteful number, since it uses less digits than its factorization.

21317517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 182220 (or 182217 counting only the distinct ones).

The product of its digits is 1470, while the sum is 27.

The square root of 21317517 is about 4617.0896677453. The cubic root of 21317517 is about 277.2759525884.

Adding to 21317517 its reverse (71571312), we get a palindrome (92888829).

The spelling of 21317517 in words is "twenty-one million, three hundred seventeen thousand, five hundred seventeen".