1991520693856 has 24 divisors (see below), whose sum is σ = 4127164597080. Its totient is φ = 943351907328.

The previous prime is 1991520693809. The next prime is 1991520693907. The reversal of 1991520693856 is 6583960251991.

It is a super-2 number, since 2×1991520693856² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1637763121 + ... + 1637764336.

It is an arithmetic number, because the mean of its divisors is an integer number (171965191545).

Almost surely, 2^{1991520693856} is an apocalyptic number.

1991520693856 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

1991520693856 is an abundant number, since it is smaller than the sum of its proper divisors (2135643903224).

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

1991520693856 is a wasteful number, since it uses less digits than its factorization.

1991520693856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3275527486 (or 3275527478 counting only the distinct ones).

The product of its (nonzero) digits is 31492800, while the sum is 64.

The spelling of 1991520693856 in words is "one trillion, nine hundred ninety-one billion, five hundred twenty million, six hundred ninety-three thousand, eight hundred fifty-six".