991916640 has 288 divisors, whose sum is σ = 3977509536. Its totient is φ = 221921280.

The previous prime is 991916593. The next prime is 991916687. The reversal of 991916640 is 46619199.

It is an interprime number because it is at equal distance from previous prime (991916593) and next prime (991916687).

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 203512 + ... + 208328.

It is an arithmetic number, because the mean of its divisors is an integer number (13810797).

Almost surely, 2^991916640 is an apocalyptic number.

991916640 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 991916640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1988754768).

991916640 is an abundant number, since it is smaller than the sum of its proper divisors (2985592896).

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

991916640 is a wasteful number, since it uses less digits than its factorization.

991916640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4862 (or 4851 counting only the distinct ones).

The product of its (nonzero) digits is 104976, while the sum is 45.

The square root of 991916640 is about 31494.7081269219. The cubic root of 991916640 is about 997.2982538079.

The spelling of 991916640 in words is "nine hundred ninety-one million, nine hundred sixteen thousand, six hundred forty".