991783581864 has 32 divisors (see below), whose sum is σ = 2546471361120. Its totient is φ = 321659539776.

The previous prime is 991783581857. The next prime is 991783581871. The reversal of 991783581864 is 468185387199.

It is an interprime number because it is at equal distance from previous prime (991783581857) and next prime (991783581871).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 558435814 + ... + 558437589.

It is an arithmetic number, because the mean of its divisors is an integer number (79577230035).

Almost surely, 2^991783581864 is an apocalyptic number.

It is an amenable number.

991783581864 is an abundant number, since it is smaller than the sum of its proper divisors (1554687779256).

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

991783581864 is a wasteful number, since it uses less digits than its factorization.

991783581864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1116873449 (or 1116873445 counting only the distinct ones).

The product of its digits is 104509440, while the sum is 69.

The spelling of 991783581864 in words is "nine hundred ninety-one billion, seven hundred eighty-three million, five hundred eighty-one thousand, eight hundred sixty-four".