66439728 has 60 divisors (see below), whose sum is σ = 186863040. Its totient is φ = 22036608.

The previous prime is 66439699. The next prime is 66439733. The reversal of 66439728 is 82793466.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 31078 + ... + 33146.

It is an arithmetic number, because the mean of its divisors is an integer number (3114384).

Almost surely, 2^66439728 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 66439728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93431520).

66439728 is an abundant number, since it is smaller than the sum of its proper divisors (120423312).

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

66439728 is a wasteful number, since it uses less digits than its factorization.

66439728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2306 (or 2297 counting only the distinct ones).

The product of its digits is 435456, while the sum is 45.

The square root of 66439728 is about 8151.0568639901. The cubic root of 66439728 is about 405.0195143775.

The spelling of 66439728 in words is "sixty-six million, four hundred thirty-nine thousand, seven hundred twenty-eight".