991017529920 has 1512 divisors, whose sum is σ = 4021299015552. Its totient is φ = 232302090240.

The previous prime is 991017529903. The next prime is 991017529949. The reversal of 991017529920 is 29925710199.

991017529920 is a `hidden beast` number, since 9 + 9 + 10 + 17 + 529 + 92 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 215 ways as a sum of consecutive naturals, for example, 11939970199 + ... + 11939970281.

It is an arithmetic number, because the mean of its divisors is an integer number (2659589296).

Almost surely, 2^991017529920 is an apocalyptic number.

991017529920 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 991017529920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2010649507776).

991017529920 is an abundant number, since it is smaller than the sum of its proper divisors (3030281485632).

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

991017529920 is an equidigital number, since it uses as much as digits as its factorization.

991017529920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193 (or 151 counting only the distinct ones).

The product of its (nonzero) digits is 918540, while the sum is 54.

The spelling of 991017529920 in words is "nine hundred ninety-one billion, seventeen million, five hundred twenty-nine thousand, nine hundred twenty".