638636201666 has 4 divisors (see below), whose sum is σ = 957954302502. Its totient is φ = 319318100832.

The previous prime is 638636201663. The next prime is 638636201737. The reversal of 638636201666 is 666102636836.

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

It can be written as a sum of positive squares in only one way, i.e., 561643826041 + 76992375625 = 749429^2 + 277475^2 .

It is not an unprimeable number, because it can be changed into a prime (638636201663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159659050415 + ... + 159659050418.

Almost surely, 2^638636201666 is an apocalyptic number.

638636201666 is a deficient number, since it is larger than the sum of its proper divisors (319318100836).

638636201666 is a wasteful number, since it uses less digits than its factorization.

638636201666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319318100835.

The product of its (nonzero) digits is 6718464, while the sum is 53.

The spelling of 638636201666 in words is "six hundred thirty-eight billion, six hundred thirty-six million, two hundred one thousand, six hundred sixty-six".