66821216716800 has 2880 divisors, whose sum is σ = 309870998236800. Its totient is φ = 13854965760000.

The previous prime is 66821216716799. The next prime is 66821216716937. The reversal of 66821216716800 is 861761212866.

It is a tau number, because it is divible by the number of its divisors (2880).

It is a super-3 number, since 3×66821216716800³ (a number of 42 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 239 ways as a sum of consecutive naturals, for example, 22266315300 + ... + 22266318300.

It is an arithmetic number, because the mean of its divisors is an integer number (107594096610).

Almost surely, 2^{66821216716800} is an apocalyptic number.

66821216716800 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 66821216716800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (154935499118400).

66821216716800 is an abundant number, since it is smaller than the sum of its proper divisors (243049781520000).

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

66821216716800 is a wasteful number, since it uses less digits than its factorization.

66821216716800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3124 (or 3090 counting only the distinct ones).

The product of its (nonzero) digits is 2322432, while the sum is 54.

The spelling of 66821216716800 in words is "sixty-six trillion, eight hundred twenty-one billion, two hundred sixteen million, seven hundred sixteen thousand, eight hundred".