661991931222336 has 5376 divisors, whose sum is σ = 2639939807232000. Its totient is φ = 155269752422400.

The previous prime is 661991931222329. The next prime is 661991931222341. The reversal of 661991931222336 is 633222139199166.

661991931222336 is a `hidden beast` number, since 6 + 6 + 1 + 9 + 91 + 9 + 312 + 223 + 3 + 6 = 666.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 767 ways as a sum of consecutive naturals, for example, 4442898867190 + ... + 4442898867338.

It is an arithmetic number, because the mean of its divisors is an integer number (491060232000).

Almost surely, 2^{661991931222336} is an apocalyptic number.

661991931222336 is a gapful number since it is divisible by the number (66) 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 661991931222336, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1319969903616000).

661991931222336 is an abundant number, since it is smaller than the sum of its proper divisors (1977947876009664).

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

661991931222336 is a wasteful number, since it uses less digits than its factorization.

661991931222336 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 398 (or 385 counting only the distinct ones).

The product of its digits is 34012224, while the sum is 63.

The spelling of 661991931222336 in words is "six hundred sixty-one trillion, nine hundred ninety-one billion, nine hundred thirty-one million, two hundred twenty-two thousand, three hundred thirty-six".