999991000020 has 96 divisors (see below), whose sum is σ = 2822400000000. Its totient is φ = 264534954624.

The previous prime is 999991000003. The next prime is 999991000103. The reversal of 999991000020 is 20000199999.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4899981 + ... + 5099979.

It is an arithmetic number, because the mean of its divisors is an integer number (29400000000).

Almost surely, 2^999991000020 is an apocalyptic number.

It is a pronic number, being equal to 999995×999996.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 999991000020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1411200000000).

999991000020 is an abundant number, since it is smaller than the sum of its proper divisors (1822408999980).

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

999991000020 is a wasteful number, since it uses less digits than its factorization.

999991000020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 200677 (or 200675 counting only the distinct ones).

The product of its (nonzero) digits is 118098, while the sum is 48.

The spelling of 999991000020 in words is "nine hundred ninety-nine billion, nine hundred ninety-one million, twenty", and thus it is an aban number.