1261637912981 has 2 divisors, whose sum is σ = 1261637912982. Its totient is φ = 1261637912980.

The previous prime is 1261637912971. The next prime is 1261637913043. The reversal of 1261637912981 is 1892197361621.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 752400108100 + 509237804881 = 867410^2 + 713609^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261637912981 - 2⁶ = 1261637912917 is a prime.

It is a super-2 number, since 2×1261637912981² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1261637912911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630818956490 + 630818956491.

It is an arithmetic number, because the mean of its divisors is an integer number (630818956491).

Almost surely, 2^{1261637912981} is an apocalyptic number.

It is an amenable number.

1261637912981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261637912981 is an equidigital number, since it uses as much as digits as its factorization.

1261637912981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1959552, while the sum is 56.

The spelling of 1261637912981 in words is "one trillion, two hundred sixty-one billion, six hundred thirty-seven million, nine hundred twelve thousand, nine hundred eighty-one".