1251263887561 has 2 divisors, whose sum is σ = 1251263887562. Its totient is φ = 1251263887560.

The previous prime is 1251263887493. The next prime is 1251263887589. The reversal of 1251263887561 is 1657883621521.

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., 963281397961 + 287982489600 = 981469^2 + 536640^2 .

It is a cyclic number.

It is not a de Polignac number, because 1251263887561 - 2²³ = 1251255498953 is a prime.

It is a super-2 number, since 2×1251263887561² (a number of 25 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1251263887591) 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, 625631943780 + 625631943781.

It is an arithmetic number, because the mean of its divisors is an integer number (625631943781).

Almost surely, 2^{1251263887561} is an apocalyptic number.

It is an amenable number.

1251263887561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1251263887561 is an equidigital number, since it uses as much as digits as its factorization.

1251263887561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4838400, while the sum is 55.

The spelling of 1251263887561 in words is "one trillion, two hundred fifty-one billion, two hundred sixty-three million, eight hundred eighty-seven thousand, five hundred sixty-one".