1991877864 has 16 divisors (see below), whose sum is σ = 4979694720. Its totient is φ = 663959280.

The previous prime is 1991877857. The next prime is 1991877887. The reversal of 1991877864 is 4687781991.

It is a junction number, because it is equal to n+sod(n) for n = 1991877798 and 1991877807.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 41497432 + ... + 41497479.

It is an arithmetic number, because the mean of its divisors is an integer number (311230920).

Almost surely, 2^1991877864 is an apocalyptic number.

It is an amenable number.

1991877864 is an abundant number, since it is smaller than the sum of its proper divisors (2987816856).

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

1991877864 is a wasteful number, since it uses less digits than its factorization.

1991877864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82994920 (or 82994916 counting only the distinct ones).

The product of its digits is 6096384, while the sum is 60.

The square root of 1991877864 is about 44630.4589266120. The cubic root of 1991877864 is about 1258.2131942121.

The spelling of 1991877864 in words is "one billion, nine hundred ninety-one million, eight hundred seventy-seven thousand, eight hundred sixty-four".