991565839440 has 1280 divisors, whose sum is σ = 4242585600000. Its totient is φ = 209695703040.

The previous prime is 991565839403. The next prime is 991565839477. The reversal of 991565839440 is 44938565199.

991565839440 is a `hidden beast` number, since 9 + 9 + 1 + 5 + 6 + 583 + 9 + 4 + 40 = 666.

It is an interprime number because it is at equal distance from previous prime (991565839403) and next prime (991565839477).

It is a hoax number, since the sum of its digits (63) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 255 ways as a sum of consecutive naturals, for example, 360699186 + ... + 360701934.

It is an arithmetic number, because the mean of its divisors is an integer number (3314520000).

Almost surely, 2^991565839440 is an apocalyptic number.

991565839440 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 991565839440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2121292800000).

991565839440 is an abundant number, since it is smaller than the sum of its proper divisors (3251019760560).

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

991565839440 is a wasteful number, since it uses less digits than its factorization.

991565839440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2865 (or 2853 counting only the distinct ones).

The product of its (nonzero) digits is 41990400, while the sum is 63.

The spelling of 991565839440 in words is "nine hundred ninety-one billion, five hundred sixty-five million, eight hundred thirty-nine thousand, four hundred forty".