66638320 has 80 divisors (see below), whose sum is σ = 186416640. Its totient is φ = 21641472.

The previous prime is 66638311. The next prime is 66638323. The reversal of 66638320 is 2383666.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66638323) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7509 + ... + 13771.

It is an arithmetic number, because the mean of its divisors is an integer number (2330208).

Almost surely, 2^66638320 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 66638320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93208320).

66638320 is an abundant number, since it is smaller than the sum of its proper divisors (119778320).

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

66638320 is a wasteful number, since it uses less digits than its factorization.

66638320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6302 (or 6296 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 34.

The square root of 66638320 is about 8163.2297529838. The cubic root of 66638320 is about 405.4226548400.

The spelling of 66638320 in words is "sixty-six million, six hundred thirty-eight thousand, three hundred twenty".