66709728 has 36 divisors (see below), whose sum is σ = 189706608. Its totient is φ = 22236480.

The previous prime is 66709723. The next prime is 66709757. The reversal of 66709728 is 82790766.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66709723) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 115528 + ... + 116103.

It is an arithmetic number, because the mean of its divisors is an integer number (5269628).

Almost surely, 2^66709728 is an apocalyptic number.

It is an amenable number.

66709728 is an abundant number, since it is smaller than the sum of its proper divisors (122996880).

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

66709728 is a wasteful number, since it uses less digits than its factorization.

66709728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 231647 (or 231636 counting only the distinct ones).

The product of its (nonzero) digits is 254016, while the sum is 45.

The square root of 66709728 is about 8167.6023409566. The cubic root of 66709728 is about 405.5674168240.

The spelling of 66709728 in words is "sixty-six million, seven hundred nine thousand, seven hundred twenty-eight".