66728640 has 224 divisors, whose sum is σ = 237012480. Its totient is φ = 15769600.

The previous prime is 66728639. The next prime is 66728657. The reversal of 66728640 is 4682766.

66728640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×66728640² = 8905422792499200, which contains 22 as substring.

It is a congruent number.

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 31 ways as a sum of consecutive naturals, for example, 749716 + ... + 749804.

Almost surely, 2^66728640 is an apocalyptic number.

66728640 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 66728640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118506240).

66728640 is an abundant number, since it is smaller than the sum of its proper divisors (170283840).

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

66728640 is a wasteful number, since it uses less digits than its factorization.

66728640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191 (or 181 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 39.

The square root of 66728640 is about 8168.7600038194. The cubic root of 66728640 is about 405.6057389024.

The spelling of 66728640 in words is "sixty-six million, seven hundred twenty-eight thousand, six hundred forty".