21015317 has 2 divisors, whose sum is σ = 21015318. Its totient is φ = 21015316.

The previous prime is 21015301. The next prime is 21015391. The reversal of 21015317 is 71351012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12453841 + 8561476 = 3529^2 + 2926^2 .

It is a cyclic number.

It is not a de Polignac number, because 21015317 - 2⁴ = 21015301 is a prime.

It is a super-2 number, since 2×21015317² = 883287097220978, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21015017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10507658 + 10507659.

It is an arithmetic number, because the mean of its divisors is an integer number (10507659).

Almost surely, 2^21015317 is an apocalyptic number.

It is an amenable number.

21015317 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015317 is an equidigital number, since it uses as much as digits as its factorization.

21015317 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 210, while the sum is 20.

The square root of 21015317 is about 4584.2466120400. The cubic root of 21015317 is about 275.9594782280.

Adding to 21015317 its reverse (71351012), we get a palindrome (92366329).

The spelling of 21015317 in words is "twenty-one million, fifteen thousand, three hundred seventeen".