66812720 has 80 divisors (see below), whose sum is σ = 177176160. Its totient is φ = 23212032.

The previous prime is 66812653. The next prime is 66812729. The reversal of 66812720 is 2721866.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (66812729) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 15791 + ... + 19569.

It is an arithmetic number, because the mean of its divisors is an integer number (2214702).

Almost surely, 2^66812720 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66812720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (88588080).

66812720 is an abundant number, since it is smaller than the sum of its proper divisors (110363440).

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

66812720 is a wasteful number, since it uses less digits than its factorization.

66812720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3822 (or 3816 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 32.

The square root of 66812720 is about 8173.9048196073. The cubic root of 66812720 is about 405.7760256879.

The spelling of 66812720 in words is "sixty-six million, eight hundred twelve thousand, seven hundred twenty".