638975999 has 4 divisors (see below), whose sum is σ = 659588160. Its totient is φ = 618363840.

The previous prime is 638975983. The next prime is 638976007. The reversal of 638975999 is 999579836.

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

It is a cyclic number.

It is not a de Polignac number, because 638975999 - 2⁴ = 638975983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638975929) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10306034 + ... + 10306095.

It is an arithmetic number, because the mean of its divisors is an integer number (164897040).

Almost surely, 2^638975999 is an apocalyptic number.

638975999 is a deficient number, since it is larger than the sum of its proper divisors (20612161).

638975999 is a wasteful number, since it uses less digits than its factorization.

638975999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20612160.

The product of its digits is 33067440, while the sum is 65.

The square root of 638975999 is about 25277.9745826283. The cubic root of 638975999 is about 861.3140174846.

It can be divided in two parts, 63897 and 5999, that added together give a palindrome (69896).

The spelling of 638975999 in words is "six hundred thirty-eight million, nine hundred seventy-five thousand, nine hundred ninety-nine".