661438800 has 180 divisors, whose sum is σ = 2504196864. Its totient is φ = 160339200.

The previous prime is 661438783. The next prime is 661438801. The reversal of 661438800 is 8834166.

It is a happy number.

661438800 is a `hidden beast` number, since 6 + 614 + 38 + 8 + 0 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (180).

It is a super-2 number, since 2×661438800² = 875002572290880000, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661438801) 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 35 ways as a sum of consecutive naturals, for example, 31249 + ... + 47951.

Almost surely, 2^661438800 is an apocalyptic number.

661438800 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 661438800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1252098432).

661438800 is an abundant number, since it is smaller than the sum of its proper divisors (1842758064).

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

661438800 is a wasteful number, since it uses less digits than its factorization.

661438800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16738 (or 16724 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 661438800 is about 25718.4525195432. The cubic root of 661438800 is about 871.2909886324.

The spelling of 661438800 in words is "six hundred sixty-one million, four hundred thirty-eight thousand, eight hundred".