661772800 has 240 divisors, whose sum is σ = 1827429912. Its totient is φ = 235929600.

The previous prime is 661772791. The next prime is 661772803. The reversal of 661772800 is 8277166.

It is a happy number.

It can be written as a sum of positive squares in 12 ways, for example, as 41165056 + 620607744 = 6416^2 + 24912^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 661772800.

It is not an unprimeable number, because it can be changed into a prime (661772803) 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 23 ways as a sum of consecutive naturals, for example, 6822352 + ... + 6822448.

Almost surely, 2^661772800 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 661772800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (913714956).

661772800 is an abundant number, since it is smaller than the sum of its proper divisors (1165657112).

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

661772800 is a wasteful number, since it uses less digits than its factorization.

661772800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 179 (or 158 counting only the distinct ones).

The product of its (nonzero) digits is 28224, while the sum is 37.

The square root of 661772800 is about 25724.9450922640. The cubic root of 661772800 is about 871.4376195935.

The spelling of 661772800 in words is "six hundred sixty-one million, seven hundred seventy-two thousand, eight hundred".