1991288319012 has 72 divisors (see below), whose sum is σ = 5047394472120. Its totient is φ = 661935697920.

The previous prime is 1991288318927. The next prime is 1991288319043. The reversal of 1991288319012 is 2109138821991.

It is a happy number.

1991288319012 is a `hidden beast` number, since 199 + 128 + 8 + 319 + 0 + 12 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 26822578176 + 1964465740836 = 163776^2 + 1401594^2 .

It is a super-2 number, since 2×1991288319012² (a number of 25 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1991288319012.

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 23 ways as a sum of consecutive naturals, for example, 110244462 + ... + 110262522.

Almost surely, 2^{1991288319012} is an apocalyptic number.

1991288319012 is a gapful number since it is divisible by the number (12) formed by its first and last digit.

It is an amenable number.

1991288319012 is an abundant number, since it is smaller than the sum of its proper divisors (3056106153108).

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

1991288319012 is a wasteful number, since it uses less digits than its factorization.

1991288319012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26333 (or 26328 counting only the distinct ones).

The product of its (nonzero) digits is 559872, while the sum is 54.

The spelling of 1991288319012 in words is "one trillion, nine hundred ninety-one billion, two hundred eighty-eight million, three hundred nineteen thousand, twelve".