1261531289 has 2 divisors, whose sum is σ = 1261531290. Its totient is φ = 1261531288.

The previous prime is 1261531261. The next prime is 1261531303. The reversal of 1261531289 is 9821351621.

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., 1089528064 + 172003225 = 33008^2 + 13115^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261531289 - 2²⁸ = 993095833 is a prime.

It is a super-2 number, since 2×1261531289² = 3182922386252003042, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1261531589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630765644 + 630765645.

It is an arithmetic number, because the mean of its divisors is an integer number (630765645).

Almost surely, 2^1261531289 is an apocalyptic number.

It is an amenable number.

1261531289 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261531289 is an equidigital number, since it uses as much as digits as its factorization.

1261531289 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 38.

The square root of 1261531289 is about 35518.0417393752. The cubic root of 1261531289 is about 1080.5196656064.

The spelling of 1261531289 in words is "one billion, two hundred sixty-one million, five hundred thirty-one thousand, two hundred eighty-nine".