1256121913 has 2 divisors, whose sum is σ = 1256121914. Its totient is φ = 1256121912.

The previous prime is 1256121833. The next prime is 1256121929. The reversal of 1256121913 is 3191216521.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1144333584 + 111788329 = 33828^2 + 10573^2 .

It is a cyclic number.

It is not a de Polignac number, because 1256121913 - 2²⁵ = 1222567481 is a prime.

It is not a weakly prime, because it can be changed into another prime (1256121983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 628060956 + 628060957.

It is an arithmetic number, because the mean of its divisors is an integer number (628060957).

Almost surely, 2^1256121913 is an apocalyptic number.

It is an amenable number.

1256121913 is a deficient number, since it is larger than the sum of its proper divisors (1).

1256121913 is an equidigital number, since it uses as much as digits as its factorization.

1256121913 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3240, while the sum is 31.

The square root of 1256121913 is about 35441.8102387561. The cubic root of 1256121913 is about 1078.9730501528.

The spelling of 1256121913 in words is "one billion, two hundred fifty-six million, one hundred twenty-one thousand, nine hundred thirteen".