638668128 has 96 divisors (see below), whose sum is σ = 2016887040. Its totient is φ = 172869120.

The previous prime is 638668123. The next prime is 638668133. The reversal of 638668128 is 821866836.

It is an interprime number because it is at equal distance from previous prime (638668123) and next prime (638668133).

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638668123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12243 + ... + 37778.

It is an arithmetic number, because the mean of its divisors is an integer number (21009240).

Almost surely, 2^638668128 is an apocalyptic number.

It is an amenable number.

638668128 is an abundant number, since it is smaller than the sum of its proper divisors (1378218912).

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

638668128 is a wasteful number, since it uses less digits than its factorization.

638668128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50060 (or 50052 counting only the distinct ones).

The product of its digits is 663552, while the sum is 48.

The square root of 638668128 is about 25271.8841402852. The cubic root of 638668128 is about 861.1756626751.

The spelling of 638668128 in words is "six hundred thirty-eight million, six hundred sixty-eight thousand, one hundred twenty-eight".