661916880 has 160 divisors (see below), whose sum is σ = 2358777600. Its totient is φ = 170408448.

The previous prime is 661916861. The next prime is 661916881. The reversal of 661916880 is 88619166.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661916881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 57357 + ... + 67923.

It is an arithmetic number, because the mean of its divisors is an integer number (14742360).

Almost surely, 2^661916880 is an apocalyptic number.

661916880 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 661916880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1179388800).

661916880 is an abundant number, since it is smaller than the sum of its proper divisors (1696860720).

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

661916880 is a wasteful number, since it uses less digits than its factorization.

661916880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10618 (or 10606 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 45.

The square root of 661916880 is about 25727.7453345605. The cubic root of 661916880 is about 871.5008576219.

The spelling of 661916880 in words is "six hundred sixty-one million, nine hundred sixteen thousand, eight hundred eighty".