1261697981 has 2 divisors, whose sum is σ = 1261697982. Its totient is φ = 1261697980.

The previous prime is 1261697977. The next prime is 1261698013. The reversal of 1261697981 is 1897961621.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1260960100 + 737881 = 35510^2 + 859^2 .

It is an emirp because it is prime and its reverse (1897961621) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1261697981 - 2² = 1261697977 is a prime.

It is a super-2 number, since 2×1261697981² = 3183763590518952722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1261697911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630848990 + 630848991.

It is an arithmetic number, because the mean of its divisors is an integer number (630848991).

Almost surely, 2^1261697981 is an apocalyptic number.

It is an amenable number.

1261697981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261697981 is an equidigital number, since it uses as much as digits as its factorization.

1261697981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 50.

The square root of 1261697981 is about 35520.3882439367. The cubic root of 1261697981 is about 1080.5672548744.

The spelling of 1261697981 in words is "one billion, two hundred sixty-one million, six hundred ninety-seven thousand, nine hundred eighty-one".