1989990999891 has 96 divisors (see below), whose sum is σ = 3058444247040. Its totient is φ = 1244782080000.

The previous prime is 1989990999881. The next prime is 1989990999907.

1989990999891 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1989990999891 - 2⁹ = 1989990999379 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1989990999811) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 2142078115 + ... + 2142079043.

It is an arithmetic number, because the mean of its divisors is an integer number (31858794240).

Almost surely, 2^{1989990999891} is an apocalyptic number.

1989990999891 is a deficient number, since it is larger than the sum of its proper divisors (1068453247149).

1989990999891 is a wasteful number, since it uses less digits than its factorization.

1989990999891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1969 (or 1966 counting only the distinct ones).

The product of its (nonzero) digits is 2754990144, while the sum is 90.

The spelling of 1989990999891 in words is "one trillion, nine hundred eighty-nine billion, nine hundred ninety million, nine hundred ninety-nine thousand, eight hundred ninety-one".