991557072 has 320 divisors, whose sum is σ = 3291217920. Its totient is φ = 283046400.

The previous prime is 991557037. The next prime is 991557089. The reversal of 991557072 is 270755199.

991557072 is a `hidden beast` number, since 9 + 9 + 1 + 5 + 570 + 72 = 666.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 7807473 + ... + 7807599.

It is an arithmetic number, because the mean of its divisors is an integer number (10285056).

Almost surely, 2^991557072 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 991557072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1645608960).

991557072 is an abundant number, since it is smaller than the sum of its proper divisors (2299660848).

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

991557072 is a wasteful number, since it uses less digits than its factorization.

991557072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 239 (or 227 counting only the distinct ones).

The product of its (nonzero) digits is 198450, while the sum is 45.

The square root of 991557072 is about 31488.9992219505. Note that the first 3 decimals coincide. The cubic root of 991557072 is about 997.1777329688.

The spelling of 991557072 in words is "nine hundred ninety-one million, five hundred fifty-seven thousand, seventy-two".