1261115591 has 2 divisors, whose sum is σ = 1261115592. Its totient is φ = 1261115590.

The previous prime is 1261115521. The next prime is 1261115629. The reversal of 1261115591 is 1955111621.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1261115591 - 2²⁶ = 1194006727 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1261115521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630557795 + 630557796.

It is an arithmetic number, because the mean of its divisors is an integer number (630557796).

Almost surely, 2^1261115591 is an apocalyptic number.

1261115591 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261115591 is an equidigital number, since it uses as much as digits as its factorization.

1261115591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2700, while the sum is 32.

The square root of 1261115591 is about 35512.1893298625. The cubic root of 1261115591 is about 1080.4009687990.

The spelling of 1261115591 in words is "one billion, two hundred sixty-one million, one hundred fifteen thousand, five hundred ninety-one".