1311111661 has 2 divisors, whose sum is σ = 1311111662. Its totient is φ = 1311111660.

The previous prime is 1311111601. The next prime is 1311111679. The reversal of 1311111661 is 1661111131.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1259185225 + 51926436 = 35485^2 + 7206^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1311111661 is a prime.

It is a super-2 number, since 2×1311111661² = 3438027575220357842, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1311111601) 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, 655555830 + 655555831.

It is an arithmetic number, because the mean of its divisors is an integer number (655555831).

Almost surely, 2^1311111661 is an apocalyptic number.

It is an amenable number.

1311111661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1311111661 is an equidigital number, since it uses as much as digits as its factorization.

1311111661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108, while the sum is 22.

The square root of 1311111661 is about 36209.2758972062. The cubic root of 1311111661 is about 1094.4936006960.

Adding to 1311111661 its reverse (1661111131), we get a palindrome (2972222792).

The spelling of 1311111661 in words is "one billion, three hundred eleven million, one hundred eleven thousand, six hundred sixty-one".