251505131209 has 2 divisors, whose sum is σ = 251505131210. Its totient is φ = 251505131208.

The previous prime is 251505131179. The next prime is 251505131231. The reversal of 251505131209 is 902131505152.

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., 146839940809 + 104665190400 = 383197^2 + 323520^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-251505131209 is a prime.

It is not a weakly prime, because it can be changed into another prime (251505131309) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125752565604 + 125752565605.

It is an arithmetic number, because the mean of its divisors is an integer number (125752565605).

Almost surely, 2^251505131209 is an apocalyptic number.

It is an amenable number.

251505131209 is a deficient number, since it is larger than the sum of its proper divisors (1).

251505131209 is an equidigital number, since it uses as much as digits as its factorization.

251505131209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13500, while the sum is 34.

The spelling of 251505131209 in words is "two hundred fifty-one billion, five hundred five million, one hundred thirty-one thousand, two hundred nine".