1999756650978 has 12 divisors (see below), whose sum is σ = 4332806077158. Its totient is φ = 666585550320.

The previous prime is 1999756650971. The next prime is 1999756650979. The reversal of 1999756650978 is 8790566579991.

1999756650978 is a `hidden beast` number, since 19 + 9 + 97 + 5 + 6 + 6 + 509 + 7 + 8 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1606548645009 + 393208005969 = 1267497^2 + 627063^2 .

It is a junction number, because it is equal to n+sod(n) for n = 1999756650897 and 1999756650906.

It is not an unprimeable number, because it can be changed into a prime (1999756650971) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 55548795843 + ... + 55548795878.

Almost surely, 2^{1999756650978} is an apocalyptic number.

1999756650978 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1999756650978 is an abundant number, since it is smaller than the sum of its proper divisors (2333049426180).

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

1999756650978 is a wasteful number, since it uses less digits than its factorization.

1999756650978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111097591729 (or 111097591726 counting only the distinct ones).

The product of its (nonzero) digits is 2314720800, while the sum is 81.

The spelling of 1999756650978 in words is "one trillion, nine hundred ninety-nine billion, seven hundred fifty-six million, six hundred fifty thousand, nine hundred seventy-eight".