1261231861 has 2 divisors, whose sum is σ = 1261231862. Its totient is φ = 1261231860.

The previous prime is 1261231847. The next prime is 1261231871. The reversal of 1261231861 is 1681321621.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1237280625 + 23951236 = 35175^2 + 4894^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261231861 - 2²³ = 1252843253 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1261231801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630615930 + 630615931.

It is an arithmetic number, because the mean of its divisors is an integer number (630615931).

Almost surely, 2^1261231861 is an apocalyptic number.

It is an amenable number.

1261231861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261231861 is an equidigital number, since it uses as much as digits as its factorization.

1261231861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3456, while the sum is 31.

The square root of 1261231861 is about 35513.8263356682. The cubic root of 1261231861 is about 1080.4341707146.

The spelling of 1261231861 in words is "one billion, two hundred sixty-one million, two hundred thirty-one thousand, eight hundred sixty-one".