661594521600 has 1620 divisors, whose sum is σ = 2724265156704. Its totient is φ = 158827806720.

The previous prime is 661594521593. The next prime is 661594521619. The reversal of 661594521600 is 6125495166.

661594521600 is a `hidden beast` number, since 6 + 6 + 1 + 594 + 52 + 1 + 6 + 0 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (1620).

It is a super-2 number, since 2×661594521600² (a number of 24 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 107 ways as a sum of consecutive naturals, for example, 28764979189 + ... + 28764979211.

Almost surely, 2^661594521600 is an apocalyptic number.

661594521600 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 661594521600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1362132578352).

661594521600 is an abundant number, since it is smaller than the sum of its proper divisors (2062670635104).

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

661594521600 is an equidigital number, since it uses as much as digits as its factorization.

661594521600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110 (or 50 counting only the distinct ones).

The product of its (nonzero) digits is 388800, while the sum is 45.

The spelling of 661594521600 in words is "six hundred sixty-one billion, five hundred ninety-four million, five hundred twenty-one thousand, six hundred".