1998792978991 has 4 divisors (see below), whose sum is σ = 2002766722992. Its totient is φ = 1994819234992.

The previous prime is 1998792978929. The next prime is 1998792978997.

1998792978991 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1998792978991 - 2⁷ = 1998792978863 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1998792978997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1986871246 + ... + 1986872251.

It is an arithmetic number, because the mean of its divisors is an integer number (500691680748).

Almost surely, 2^{1998792978991} is an apocalyptic number.

1998792978991 is a deficient number, since it is larger than the sum of its proper divisors (3973744001).

1998792978991 is an equidigital number, since it uses as much as digits as its factorization.

1998792978991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3973744000.

The product of its digits is 3333197952, while the sum is 88.

The spelling of 1998792978991 in words is "one trillion, nine hundred ninety-eight billion, seven hundred ninety-two million, nine hundred seventy-eight thousand, nine hundred ninety-one".