661312800 has 216 divisors, whose sum is σ = 2377324404. Its totient is φ = 172922880.

The previous prime is 661312789. The next prime is 661312807. The reversal of 661312800 is 8213166.

It can be written as a sum of positive squares in 6 ways, for example, as 294053904 + 367258896 = 17148^2 + 19164^2 .

It is not an unprimeable number, because it can be changed into a prime (661312807) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 380734 + ... + 382466.

Almost surely, 2^661312800 is an apocalyptic number.

661312800 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 661312800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1188662202).

661312800 is an abundant number, since it is smaller than the sum of its proper divisors (1716011604).

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

661312800 is a wasteful number, since it uses less digits than its factorization.

661312800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1812 (or 1796 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 661312800 is about 25716.0027998132. The cubic root of 661312800 is about 871.2356599377.

Adding to 661312800 its reverse (8213166), we get a palindrome (669525966).

The spelling of 661312800 in words is "six hundred sixty-one million, three hundred twelve thousand, eight hundred".