12817921 has 2 divisors, whose sum is σ = 12817922. Its totient is φ = 12817920.

The previous prime is 12817907. The next prime is 12817933. The reversal of 12817921 is 12971821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12816400 + 1521 = 3580^2 + 39^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12817921 is a prime.

It is not a weakly prime, because it can be changed into another prime (12817421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6408960 + 6408961.

It is an arithmetic number, because the mean of its divisors is an integer number (6408961).

Almost surely, 2^12817921 is an apocalyptic number.

It is an amenable number.

12817921 is a deficient number, since it is larger than the sum of its proper divisors (1).

12817921 is an equidigital number, since it uses as much as digits as its factorization.

12817921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2016, while the sum is 31.

The square root of 12817921 is about 3580.2124238654. The cubic root of 12817921 is about 234.0305375686.

The spelling of 12817921 in words is "twelve million, eight hundred seventeen thousand, nine hundred twenty-one".