661644884160 has 1120 divisors, whose sum is σ = 2647415941632. Its totient is φ = 155748925440.

The previous prime is 661644884143. The next prime is 661644884161. The reversal of 661644884160 is 61488446166.

661644884160 is a `hidden beast` number, since 6 + 6 + 1 + 64 + 488 + 41 + 60 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a junction number, because it is equal to n+sod(n) for n = 661644884097 and 661644884106.

It is not an unprimeable number, because it can be changed into a prime (661644884161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 1013238394 + ... + 1013239046.

Almost surely, 2^661644884160 is an apocalyptic number.

661644884160 is a gapful number since it is divisible by the number (60) 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 661644884160, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1323707970816).

661644884160 is an abundant number, since it is smaller than the sum of its proper divisors (1985771057472).

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

661644884160 is a wasteful number, since it uses less digits than its factorization.

661644884160 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 823 (or 804 counting only the distinct ones).

The product of its (nonzero) digits is 5308416, while the sum is 54.

The spelling of 661644884160 in words is "six hundred sixty-one billion, six hundred forty-four million, eight hundred eighty-four thousand, one hundred sixty".