66655680 has 336 divisors, whose sum is σ = 267553440. Its totient is φ = 13934592.

The previous prime is 66655669. The next prime is 66655681. The reversal of 66655680 is 8655666.

66655680 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (336).

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66655681) 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 47 ways as a sum of consecutive naturals, for example, 611466 + ... + 611574.

It is an arithmetic number, because the mean of its divisors is an integer number (796290).

Almost surely, 2^66655680 is an apocalyptic number.

66655680 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 66655680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (133776720).

66655680 is an abundant number, since it is smaller than the sum of its proper divisors (200897760).

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

66655680 is a wasteful number, since it uses less digits than its factorization.

66655680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156 (or 139 counting only the distinct ones).

The product of its (nonzero) digits is 259200, while the sum is 42.

The square root of 66655680 is about 8164.2929883732. The cubic root of 66655680 is about 405.4578574392.

The spelling of 66655680 in words is "sixty-six million, six hundred fifty-five thousand, six hundred eighty".