661668864 has 88 divisors (see below), whose sum is σ = 1804962720. Its totient is φ = 215384064.

The previous prime is 661668827. The next prime is 661668869. The reversal of 661668864 is 468866166.

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

It is not an unprimeable number, because it can be changed into a prime (661668869) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 129592 + ... + 134600.

It is an arithmetic number, because the mean of its divisors is an integer number (20510940).

Almost surely, 2^661668864 is an apocalyptic number.

661668864 is a gapful number since it is divisible by the number (64) 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 661668864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (902481360).

661668864 is an abundant number, since it is smaller than the sum of its proper divisors (1143293856).

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

661668864 is a wasteful number, since it uses less digits than its factorization.

661668864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5075 (or 5057 counting only the distinct ones).

The product of its digits is 1990656, while the sum is 51.

The square root of 661668864 is about 25722.9248725723. The cubic root of 661668864 is about 871.3919954344.

The spelling of 661668864 in words is "six hundred sixty-one million, six hundred sixty-eight thousand, eight hundred sixty-four".