66608721 has 12 divisors (see below), whose sum is σ = 97568640. Its totient is φ = 43779960.

The previous prime is 66608681. The next prime is 66608749. The reversal of 66608721 is 12780666.

It is a happy number.

It is not a de Polignac number, because 66608721 - 2⁷ = 66608593 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66608791) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 51481 + ... + 52758.

It is an arithmetic number, because the mean of its divisors is an integer number (8130720).

Almost surely, 2^66608721 is an apocalyptic number.

It is an amenable number.

66608721 is a deficient number, since it is larger than the sum of its proper divisors (30959919).

66608721 is a wasteful number, since it uses less digits than its factorization.

66608721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104316 (or 104313 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 66608721 is about 8161.4166049773. The cubic root of 66608721 is about 405.3626199016.

The spelling of 66608721 in words is "sixty-six million, six hundred eight thousand, seven hundred twenty-one".