66561748800 has 84 divisors (see below), whose sum is σ = 218378019936. Its totient is φ = 17749798400.

The previous prime is 66561748769. The next prime is 66561748811. The reversal of 66561748800 is 884716566.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6928716 + ... + 6938315.

Almost surely, 2^66561748800 is an apocalyptic number.

66561748800 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66561748800 is an abundant number, since it is smaller than the sum of its proper divisors (151816271136).

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

66561748800 is a wasteful number, since it uses less digits than its factorization.

66561748800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13867056 (or 13867041 counting only the distinct ones).

The product of its (nonzero) digits is 1935360, while the sum is 51.

It can be divided in two parts, 665617 and 48800, that added together give a palindrome (714417).

The spelling of 66561748800 in words is "sixty-six billion, five hundred sixty-one million, seven hundred forty-eight thousand, eight hundred".