1991911738842 has 64 divisors (see below), whose sum is σ = 4587465093120. Its totient is φ = 639992070000.

The previous prime is 1991911738793. The next prime is 1991911738931. The reversal of 1991911738842 is 2488371191991.

1991911738842 is a `hidden beast` number, since 1 + 99 + 19 + 117 + 388 + 42 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 1991911738842.

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 31 ways as a sum of consecutive naturals, for example, 1950168 + ... + 2790515.

It is an arithmetic number, because the mean of its divisors is an integer number (71679142080).

Almost surely, 2^{1991911738842} is an apocalyptic number.

1991911738842 is an abundant number, since it is smaller than the sum of its proper divisors (2595553354278).

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

1991911738842 is a wasteful number, since it uses less digits than its factorization.

1991911738842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4740976 (or 4740970 counting only the distinct ones).

The product of its digits is 7838208, while the sum is 63.

The spelling of 1991911738842 in words is "one trillion, nine hundred ninety-one billion, nine hundred eleven million, seven hundred thirty-eight thousand, eight hundred forty-two".