1251561134209 has 2 divisors, whose sum is σ = 1251561134210. Its totient is φ = 1251561134208.

The previous prime is 1251561134191. The next prime is 1251561134251. The reversal of 1251561134209 is 9024311651521.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1222565855809 + 28995278400 = 1105697^2 + 170280^2 .

It is a cyclic number.

It is not a de Polignac number, because 1251561134209 - 2⁷ = 1251561134081 is a prime.

It is not a weakly prime, because it can be changed into another prime (1251561137209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 625780567104 + 625780567105.

It is an arithmetic number, because the mean of its divisors is an integer number (625780567105).

Almost surely, 2^{1251561134209} is an apocalyptic number.

It is an amenable number.

1251561134209 is a deficient number, since it is larger than the sum of its proper divisors (1).

1251561134209 is an equidigital number, since it uses as much as digits as its factorization.

1251561134209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64800, while the sum is 40.

The spelling of 1251561134209 in words is "one trillion, two hundred fifty-one billion, five hundred sixty-one million, one hundred thirty-four thousand, two hundred nine".