1261331989 has 2 divisors, whose sum is σ = 1261331990. Its totient is φ = 1261331988.

The previous prime is 1261331987. The next prime is 1261332013. The reversal of 1261331989 is 9891331621.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 906311025 + 355020964 = 30105^2 + 18842^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261331989 - 2¹ = 1261331987 is a prime.

It is a super-2 number, since 2×1261331989² = 3181916772949392242, which contains 22 as substring.

Together with 1261331987, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1261331987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630665994 + 630665995.

It is an arithmetic number, because the mean of its divisors is an integer number (630665995).

Almost surely, 2^1261331989 is an apocalyptic number.

It is an amenable number.

1261331989 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261331989 is an equidigital number, since it uses as much as digits as its factorization.

1261331989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69984, while the sum is 43.

The square root of 1261331989 is about 35515.2360121681. The cubic root of 1261331989 is about 1080.4627615057.

The spelling of 1261331989 in words is "one billion, two hundred sixty-one million, three hundred thirty-one thousand, nine hundred eighty-nine".