66781920 has 72 divisors (see below), whose sum is σ = 210928536. Its totient is φ = 17760768.

The previous prime is 66781909. The next prime is 66781921. The reversal of 66781920 is 2918766.

66781920 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66781921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 178854 + ... + 179226.

It is an arithmetic number, because the mean of its divisors is an integer number (2929563).

Almost surely, 2^66781920 is an apocalyptic number.

66781920 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 66781920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105464268).

66781920 is an abundant number, since it is smaller than the sum of its proper divisors (144146616).

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

66781920 is an equidigital number, since it uses as much as digits as its factorization.

66781920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 764 (or 383 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 39.

The square root of 66781920 is about 8172.0205579771. The cubic root of 66781920 is about 405.7136631989.

The spelling of 66781920 in words is "sixty-six million, seven hundred eighty-one thousand, nine hundred twenty".