1991779967892 has 96 divisors (see below), whose sum is σ = 5460307332480. Its totient is φ = 557108282880.

The previous prime is 1991779967869. The next prime is 1991779967929. The reversal of 1991779967892 is 2987699771991.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 51510438 + ... + 51549090.

It is an arithmetic number, because the mean of its divisors is an integer number (56878201380).

Almost surely, 2^{1991779967892} is an apocalyptic number.

1991779967892 is a gapful number since it is divisible by the number (12) formed by its first and last digit.

It is an amenable number.

1991779967892 is an abundant number, since it is smaller than the sum of its proper divisors (3468527364588).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1991779967892 is a wasteful number, since it uses less digits than its factorization.

1991779967892 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68713 (or 68711 counting only the distinct ones).

The product of its digits is 1944365472, while the sum is 84.

The spelling of 1991779967892 in words is "one trillion, nine hundred ninety-one billion, seven hundred seventy-nine million, nine hundred sixty-seven thousand, eight hundred ninety-two".