661207680 has 576 divisors, whose sum is σ = 2815787520. Its totient is φ = 139898880.

The previous prime is 661207663. The next prime is 661207691. The reversal of 661207680 is 86702166.

It is a happy number.

661207680 is an esthetic number in base 5, because in such base its adjacent digits differ by 1.

It is a tau number, because it is divible by the number of its divisors (576).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

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 71 ways as a sum of consecutive naturals, for example, 21329265 + ... + 21329295.

It is an arithmetic number, because the mean of its divisors is an integer number (4888520).

Almost surely, 2^661207680 is an apocalyptic number.

661207680 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 661207680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1407893760).

661207680 is an abundant number, since it is smaller than the sum of its proper divisors (2154579840).

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

661207680 is a wasteful number, since it uses less digits than its factorization.

661207680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 109 (or 71 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 661207680 is about 25713.9588550655. The cubic root of 661207680 is about 871.1894946204.

The spelling of 661207680 in words is "six hundred sixty-one million, two hundred seven thousand, six hundred eighty".