66805920 has 144 divisors (see below), whose sum is σ = 241473960. Its totient is φ = 16760832.

The previous prime is 66805913. The next prime is 66805931. The reversal of 66805920 is 2950866.

66805920 is a `hidden beast` number, since 6 + 68 + 0 + 592 + 0 = 666.

66805920 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 66781584 + 24336 = 8172^2 + 156^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 23116 + ... + 25844.

Almost surely, 2^66805920 is an apocalyptic number.

66805920 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 66805920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (120736980).

66805920 is an abundant number, since it is smaller than the sum of its proper divisors (174668040).

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

66805920 is a wasteful number, since it uses less digits than its factorization.

66805920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2767 (or 2756 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The square root of 66805920 is about 8173.4888511577. The cubic root of 66805920 is about 405.7622589950.

The spelling of 66805920 in words is "sixty-six million, eight hundred five thousand, nine hundred twenty".