66639906 has 24 divisors (see below), whose sum is σ = 145312284. Its totient is φ = 22070880.

The previous prime is 66639893. The next prime is 66639913. The reversal of 66639906 is 60993666.

66639906 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 63345681 + 3294225 = 7959^2 + 1815^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8965 + ... + 14616.

Almost surely, 2^66639906 is an apocalyptic number.

66639906 is an abundant number, since it is smaller than the sum of its proper divisors (78672378).

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

66639906 is a wasteful number, since it uses less digits than its factorization.

66639906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23746 (or 23743 counting only the distinct ones).

The product of its (nonzero) digits is 314928, while the sum is 45.

The square root of 66639906 is about 8163.3268953289. The cubic root of 66639906 is about 405.4258711838.

The spelling of 66639906 in words is "sixty-six million, six hundred thirty-nine thousand, nine hundred six".