21131317 has 2 divisors, whose sum is σ = 21131318. Its totient is φ = 21131316.

The previous prime is 21131293. The next prime is 21131333. The reversal of 21131317 is 71313112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18438436 + 2692881 = 4294^2 + 1641^2 .

It is a cyclic number.

It is not a de Polignac number, because 21131317 - 2¹⁹ = 20607029 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21131294 and 21131303.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21132317) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10565658 + 10565659.

It is an arithmetic number, because the mean of its divisors is an integer number (10565659).

Almost surely, 2^21131317 is an apocalyptic number.

It is an amenable number.

21131317 is a deficient number, since it is larger than the sum of its proper divisors (1).

21131317 is an equidigital number, since it uses as much as digits as its factorization.

21131317 is an evil number, because the sum of its binary digits is even.

The product of its digits is 126, while the sum is 19.

The square root of 21131317 is about 4596.8812253527. The cubic root of 21131317 is about 276.4662923919.

Adding to 21131317 its reverse (71313112), we get a palindrome (92444429).

The spelling of 21131317 in words is "twenty-one million, one hundred thirty-one thousand, three hundred seventeen".