1261557361 has 2 divisors, whose sum is σ = 1261557362. Its totient is φ = 1261557360.

The previous prime is 1261557343. The next prime is 1261557371. The reversal of 1261557361 is 1637551621.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1023040225 + 238517136 = 31985^2 + 15444^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261557361 - 2¹⁷ = 1261426289 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1261557361.

It is not a weakly prime, because it can be changed into another prime (1261557371) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630778680 + 630778681.

It is an arithmetic number, because the mean of its divisors is an integer number (630778681).

Almost surely, 2^1261557361 is an apocalyptic number.

It is an amenable number.

1261557361 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261557361 is an equidigital number, since it uses as much as digits as its factorization.

1261557361 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37800, while the sum is 37.

The square root of 1261557361 is about 35518.4087622179. The cubic root of 1261557361 is about 1080.5271092360.

The spelling of 1261557361 in words is "one billion, two hundred sixty-one million, five hundred fifty-seven thousand, three hundred sixty-one".