66665638 has 48 divisors (see below), whose sum is σ = 116501616. Its totient is φ = 28416960.

The previous prime is 66665633. The next prime is 66665647. The reversal of 66665638 is 83656666.

It is a Harshad number since it is a multiple of its sum of digits (46).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66665633) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 508833 + ... + 508963.

It is an arithmetic number, because the mean of its divisors is an integer number (2427117).

Almost surely, 2^66665638 is an apocalyptic number.

66665638 is a deficient number, since it is larger than the sum of its proper divisors (49835978).

66665638 is a wasteful number, since it uses less digits than its factorization.

66665638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 229 (or 206 counting only the distinct ones).

The product of its digits is 933120, while the sum is 46.

The square root of 66665638 is about 8164.9028163230. The cubic root of 66665638 is about 405.4780475080.

66665638 divided by its sum of digits (46) gives a triangular number (1449253 = T₁₇₀₂).

The spelling of 66665638 in words is "sixty-six million, six hundred sixty-five thousand, six hundred thirty-eight".