1291731899 has 4 divisors (see below), whose sum is σ = 1313625720. Its totient is φ = 1269838080.

The previous prime is 1291731877. The next prime is 1291731941. The reversal of 1291731899 is 9981371921.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9981371921 = 241 ⋅41416481.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1291731899 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1291731829) 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 in 3 ways as a sum of consecutive naturals, for example, 10946822 + ... + 10946939.

It is an arithmetic number, because the mean of its divisors is an integer number (328406430).

Almost surely, 2^1291731899 is an apocalyptic number.

1291731899 is a deficient number, since it is larger than the sum of its proper divisors (21893821).

1291731899 is an equidigital number, since it uses as much as digits as its factorization.

1291731899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21893820.

The product of its digits is 244944, while the sum is 50.

The square root of 1291731899 is about 35940.6719330621. The cubic root of 1291731899 is about 1089.0741792027.

It can be divided in two parts, 129173 and 1899, that added together give a 17-th power (131072 = 2¹⁷).

The spelling of 1291731899 in words is "one billion, two hundred ninety-one million, seven hundred thirty-one thousand, eight hundred ninety-nine".