66721853520 has 720 divisors, whose sum is σ = 274157542080. Its totient is φ = 14868209664.

The previous prime is 66721853509. The next prime is 66721853599. The reversal of 66721853520 is 2535812766.

66721853520 is a `hidden beast` number, since 6 + 6 + 72 + 1 + 8 + 53 + 520 = 666.

It is a tau number, because it is divible by the number of its divisors (720).

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 (17) of ones.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 687854112 + ... + 687854208.

It is an arithmetic number, because the mean of its divisors is an integer number (380774364).

Almost surely, 2^66721853520 is an apocalyptic number.

66721853520 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 66721853520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (137078771040).

66721853520 is an abundant number, since it is smaller than the sum of its proper divisors (207435688560).

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

66721853520 is a wasteful number, since it uses less digits than its factorization.

66721853520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 297 (or 181 counting only the distinct ones).

The product of its (nonzero) digits is 604800, while the sum is 45.

The spelling of 66721853520 in words is "sixty-six billion, seven hundred twenty-one million, eight hundred fifty-three thousand, five hundred twenty".