66997728 has 144 divisors (see below), whose sum is σ = 220147200. Its totient is φ = 18931968.

The previous prime is 66997717. The next prime is 66997739. The reversal of 66997728 is 82779966.

It is an interprime number because it is at equal distance from previous prime (66997717) and next prime (66997739).

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

It is a nude number because it is divisible by every one of its digits.

Its product of digits (2286144) is a multiple of the sum of its prime divisors (378).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 336573 + ... + 336771.

It is an arithmetic number, because the mean of its divisors is an integer number (1528800).

Almost surely, 2^66997728 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 66997728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (110073600).

66997728 is an abundant number, since it is smaller than the sum of its proper divisors (153149472).

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

66997728 is a wasteful number, since it uses less digits than its factorization.

66997728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 389 (or 378 counting only the distinct ones).

The product of its digits is 2286144, while the sum is 54.

The square root of 66997728 is about 8185.2139862071. The cubic root of 66997728 is about 406.1502190289.

The spelling of 66997728 in words is "sixty-six million, nine hundred ninety-seven thousand, seven hundred twenty-eight".