1999991131 has 2 divisors, whose sum is σ = 1999991132. Its totient is φ = 1999991130.

The previous prime is 1999991113. The next prime is 1999991153. The reversal of 1999991131 is 1311999991.

Together with previous prime (1999991113) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1999991131 - 2⁵ = 1999991099 is a prime.

It is a super-2 number, since 2×1999991131² = 7999929048157318322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1999995131) 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, 999995565 + 999995566.

It is an arithmetic number, because the mean of its divisors is an integer number (999995566).

Almost surely, 2^1999991131 is an apocalyptic number.

1999991131 is a deficient number, since it is larger than the sum of its proper divisors (1).

1999991131 is an equidigital number, since it uses as much as digits as its factorization.

1999991131 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 177147, while the sum is 52.

The square root of 1999991131 is about 44721.2603914514. The cubic root of 1999991131 is about 1259.9191875188.

The spelling of 1999991131 in words is "one billion, nine hundred ninety-nine million, nine hundred ninety-one thousand, one hundred thirty-one".