991557504 has 256 divisors, whose sum is σ = 3542745600. Its totient is φ = 266526720.

The previous prime is 991557461. The next prime is 991557517. The reversal of 991557504 is 405755199.

991557504 is a `hidden beast` number, since 9 + 91 + 5 + 57 + 504 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 991557504.

It is a congruent number.

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, 410059 + ... + 412469.

It is an arithmetic number, because the mean of its divisors is an integer number (13838850).

Almost surely, 2^991557504 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 991557504, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1771372800).

991557504 is an abundant number, since it is smaller than the sum of its proper divisors (2551188096).

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

991557504 is a wasteful number, since it uses less digits than its factorization.

991557504 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2458 (or 2440 counting only the distinct ones).

The product of its (nonzero) digits is 283500, while the sum is 45.

The square root of 991557504 is about 31489.0060814882. The cubic root of 991557504 is about 997.1778777850.

The spelling of 991557504 in words is "nine hundred ninety-one million, five hundred fifty-seven thousand, five hundred four".