991559556 has 96 divisors (see below), whose sum is σ = 2802956800. Its totient is φ = 305060256.

The previous prime is 991559549. The next prime is 991559587. The reversal of 991559556 is 655955199.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

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 31 ways as a sum of consecutive naturals, for example, 109365 + ... + 118083.

Almost surely, 2^991559556 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 991559556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1401478400).

991559556 is an abundant number, since it is smaller than the sum of its proper divisors (1811397244).

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

991559556 is a wasteful number, since it uses less digits than its factorization.

991559556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8757 (or 8737 counting only the distinct ones).

The product of its digits is 2733750, while the sum is 54.

The square root of 991559556 is about 31489.0386642717. The cubic root of 991559556 is about 997.1785656616.

The spelling of 991559556 in words is "nine hundred ninety-one million, five hundred fifty-nine thousand, five hundred fifty-six".