661388375952 has 180 divisors, whose sum is σ = 1928298878220. Its totient is φ = 219747520512.

The previous prime is 661388375939. The next prime is 661388375953. The reversal of 661388375952 is 259573883166.

661388375952 is a `hidden beast` number, since 6 + 6 + 1 + 3 + 8 + 8 + 37 + 595 + 2 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 250256065536 + 411132310416 = 500256^2 + 641196^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 661388375952.

It is not an unprimeable number, because it can be changed into a prime (661388375953) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 32847424 + ... + 32867552.

Almost surely, 2^661388375952 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661388375952, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (964149439110).

661388375952 is an abundant number, since it is smaller than the sum of its proper divisors (1266910502268).

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

661388375952 is an equidigital number, since it uses as much as digits as its factorization.

661388375952 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20474 (or 20447 counting only the distinct ones).

The product of its digits is 65318400, while the sum is 63.

The spelling of 661388375952 in words is "six hundred sixty-one billion, three hundred eighty-eight million, three hundred seventy-five thousand, nine hundred fifty-two".