1991291399 has 2 divisors, whose sum is σ = 1991291400. Its totient is φ = 1991291398.

The previous prime is 1991291377. The next prime is 1991291513. The reversal of 1991291399 is 9931921991.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1991291399 - 2²⁴ = 1974514183 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1991291399.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991291329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995645699 + 995645700.

It is an arithmetic number, because the mean of its divisors is an integer number (995645700).

Almost surely, 2^1991291399 is an apocalyptic number.

1991291399 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991291399 is an equidigital number, since it uses as much as digits as its factorization.

1991291399 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 354294, while the sum is 53.

The square root of 1991291399 is about 44623.8882102400. Note that the first 3 decimals coincide. The cubic root of 1991291399 is about 1258.0896976120.

The spelling of 1991291399 in words is "one billion, nine hundred ninety-one million, two hundred ninety-one thousand, three hundred ninety-nine".