991974392640 has 3360 divisors, whose sum is σ = 4888889343360. Its totient is φ = 188116992000.

The previous prime is 991974392593. The next prime is 991974392699. The reversal of 991974392640 is 46293479199.

991974392640 is a `hidden beast` number, since 9 + 9 + 197 + 439 + 2 + 6 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (3360).

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 479 ways as a sum of consecutive naturals, for example, 9821528590 + ... + 9821528690.

Almost surely, 2^991974392640 is an apocalyptic number.

991974392640 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 991974392640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2444444671680).

991974392640 is an abundant number, since it is smaller than the sum of its proper divisors (3896914950720).

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

991974392640 is a wasteful number, since it uses less digits than its factorization.

991974392640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 211 (or 185 counting only the distinct ones).

The product of its (nonzero) digits is 26453952, while the sum is 63.

The spelling of 991974392640 in words is "nine hundred ninety-one billion, nine hundred seventy-four million, three hundred ninety-two thousand, six hundred forty".