991868208 has 80 divisors (see below), whose sum is σ = 2664874080. Its totient is φ = 317513728.

The previous prime is 991868197. The next prime is 991868209. The reversal of 991868208 is 802868199.

It is a super-2 number, since 2×991868208² = 1967605084082262528, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (991868209) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 272416 + ... + 276032.

It is an arithmetic number, because the mean of its divisors is an integer number (33310926).

Almost surely, 2^991868208 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 991868208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1332437040).

991868208 is an abundant number, since it is smaller than the sum of its proper divisors (1673005872).

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

991868208 is a wasteful number, since it uses less digits than its factorization.

991868208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3854 (or 3848 counting only the distinct ones).

The product of its (nonzero) digits is 497664, while the sum is 51.

The square root of 991868208 is about 31493.9392264607. The cubic root of 991868208 is about 997.2820219549.

The spelling of 991868208 in words is "nine hundred ninety-one million, eight hundred sixty-eight thousand, two hundred eight".