991708557840 has 2880 divisors, whose sum is σ = 4988092741632. Its totient is φ = 172788940800.

The previous prime is 991708557839. The next prime is 991708557859. The reversal of 991708557840 is 48755807199.

991708557840 is a `hidden beast` number, since 9 + 9 + 1 + 70 + 8 + 557 + 8 + 4 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is an unprimeable number.

It is a polite number, since it can be written in 575 ways as a sum of consecutive naturals, for example, 2658735894 + ... + 2658736266.

Almost surely, 2^991708557840 is an apocalyptic number.

991708557840 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 991708557840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2494046370816).

991708557840 is an abundant number, since it is smaller than the sum of its proper divisors (3996384183792).

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

991708557840 is a wasteful number, since it uses less digits than its factorization.

991708557840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 478 (or 462 counting only the distinct ones).

The product of its (nonzero) digits is 25401600, while the sum is 63.

The spelling of 991708557840 in words is "nine hundred ninety-one billion, seven hundred eight million, five hundred fifty-seven thousand, eight hundred forty".