1331185781 has 2 divisors, whose sum is σ = 1331185782. Its totient is φ = 1331185780.

The previous prime is 1331185763. The next prime is 1331185783. The reversal of 1331185781 is 1875811331.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1076496100 + 254689681 = 32810^2 + 15959^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1331185781 is a prime.

It is a super-2 number, since 2×1331185781² = 3544111167073159922, which contains 22 as substring.

Together with 1331185783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1331185783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 665592890 + 665592891.

It is an arithmetic number, because the mean of its divisors is an integer number (665592891).

Almost surely, 2^1331185781 is an apocalyptic number.

It is an amenable number.

1331185781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1331185781 is an equidigital number, since it uses as much as digits as its factorization.

1331185781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20160, while the sum is 38.

The square root of 1331185781 is about 36485.4187450274. The cubic root of 1331185781 is about 1100.0511769578.

The spelling of 1331185781 in words is "one billion, three hundred thirty-one million, one hundred eighty-five thousand, seven hundred eighty-one".