1311991824581 has 2 divisors, whose sum is σ = 1311991824582. Its totient is φ = 1311991824580.

The previous prime is 1311991824553. The next prime is 1311991824617. The reversal of 1311991824581 is 1854281991131.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1268450325025 + 43541499556 = 1126255^2 + 208666^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1311991824581 is a prime.

It is a super-3 number, since 3×1311991824581³ (a number of 37 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1311991824881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 655995912290 + 655995912291.

It is an arithmetic number, because the mean of its divisors is an integer number (655995912291).

Almost surely, 2^{1311991824581} is an apocalyptic number.

It is an amenable number.

1311991824581 is a deficient number, since it is larger than the sum of its proper divisors (1).

1311991824581 is an equidigital number, since it uses as much as digits as its factorization.

1311991824581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 622080, while the sum is 53.

The spelling of 1311991824581 in words is "one trillion, three hundred eleven billion, nine hundred ninety-one million, eight hundred twenty-four thousand, five hundred eighty-one".