66666638 has 4 divisors (see below), whose sum is σ = 99999960. Its totient is φ = 33333318.

The previous prime is 66666631. The next prime is 66666643. The reversal of 66666638 is 83666666.

66666638 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a junction number, because it is equal to n+sod(n) for n = 66666592 and 66666601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66666631) by changing a digit.

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 as a sum of consecutive naturals, namely, 16666658 + ... + 16666661.

It is an arithmetic number, because the mean of its divisors is an integer number (24999990).

Almost surely, 2^66666638 is an apocalyptic number.

66666638 is a deficient number, since it is larger than the sum of its proper divisors (33333322).

66666638 is a wasteful number, since it uses less digits than its factorization.

66666638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33333321.

The product of its digits is 1119744, while the sum is 47.

The square root of 66666638 is about 8164.9640538094. The cubic root of 66666638 is about 405.4800749194.

The spelling of 66666638 in words is "sixty-six million, six hundred sixty-six thousand, six hundred thirty-eight".