1331031991 has 2 divisors, whose sum is σ = 1331031992. Its totient is φ = 1331031990.

The previous prime is 1331031973. The next prime is 1331032039. The reversal of 1331031991 is 1991301331.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1331031991 - 2¹⁵ = 1330999223 is a prime.

It is a super-2 number, since 2×1331031991² = 3543292322130848162, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1331031941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 665515995 + 665515996.

It is an arithmetic number, because the mean of its divisors is an integer number (665515996).

Almost surely, 2^1331031991 is an apocalyptic number.

1331031991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1331031991 is an equidigital number, since it uses as much as digits as its factorization.

1331031991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2187, while the sum is 31.

The square root of 1331031991 is about 36483.3111298851. The cubic root of 1331031991 is about 1100.0088128771.

The spelling of 1331031991 in words is "one billion, three hundred thirty-one million, thirty-one thousand, nine hundred ninety-one".