20856317 has 2 divisors, whose sum is σ = 20856318. Its totient is φ = 20856316.

The previous prime is 20856259. The next prime is 20856347. The reversal of 20856317 is 71365802.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15570916 + 5285401 = 3946^2 + 2299^2 .

It is a cyclic number.

It is not a de Polignac number, because 20856317 - 2⁸ = 20856061 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20856347) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10428158 + 10428159.

It is an arithmetic number, because the mean of its divisors is an integer number (10428159).

Almost surely, 2^20856317 is an apocalyptic number.

It is an amenable number.

20856317 is a deficient number, since it is larger than the sum of its proper divisors (1).

20856317 is an equidigital number, since it uses as much as digits as its factorization.

20856317 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 20856317 is about 4566.8716863954. The cubic root of 20856317 is about 275.2617540806.

The spelling of 20856317 in words is "twenty million, eight hundred fifty-six thousand, three hundred seventeen".