1990391866991 has 8 divisors (see below), whose sum is σ = 2171568254544. Its totient is φ = 1809254091520.

The previous prime is 1990391866919. The next prime is 1990391867071. The reversal of 1990391866991 is 1996681930991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1990391866991 - 2²² = 1990387672687 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 (1990391866391) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9545180 + ... + 9751473.

It is an arithmetic number, because the mean of its divisors is an integer number (271446031818).

Almost surely, 2^{1990391866991} is an apocalyptic number.

1990391866991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1990391866991 is a deficient number, since it is larger than the sum of its proper divisors (181176387553).

1990391866991 is a wasteful number, since it uses less digits than its factorization.

1990391866991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19306041.

The product of its (nonzero) digits is 51018336, while the sum is 71.

The spelling of 1990391866991 in words is "one trillion, nine hundred ninety billion, three hundred ninety-one million, eight hundred sixty-six thousand, nine hundred ninety-one".