991009000000 has 98 divisors (see below), whose sum is σ = 2458137871370. Its totient is φ = 396403200000.

The previous prime is 991008999983. The next prime is 991009000019. The reversal of 991009000000 is 900199.

991009000000 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 7 ways, for example, as 971155062784 + 19853937216 = 985472^2 + 140904^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 504496 + ... + 1495504.

Almost surely, 2^991009000000 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 991009000000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1229068935685).

991009000000 is an abundant number, since it is smaller than the sum of its proper divisors (1467128871370).

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

991009000000 is an frugal number, since it uses more digits than its factorization.

991009000000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 991051 (or 991016 counting only the distinct ones).

The product of its (nonzero) digits is 729, while the sum is 28.

Adding to 991009000000 its reverse (900199), we get a palindrome (991009900199).

The spelling of 991009000000 in words is "nine hundred ninety-one billion, nine million", and thus it is an aban number.