638643169 has 4 divisors (see below), whose sum is σ = 639258880. Its totient is φ = 638027460.

The previous prime is 638643151. The next prime is 638643193. The reversal of 638643169 is 961346836.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 638643169 - 2¹¹ = 638641121 is a prime.

It is a super-2 number, since 2×638643169² = 815730194620725122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638643119) 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, 306297 + ... + 308374.

It is an arithmetic number, because the mean of its divisors is an integer number (159814720).

Almost surely, 2^638643169 is an apocalyptic number.

It is an amenable number.

638643169 is a deficient number, since it is larger than the sum of its proper divisors (615711).

638643169 is a wasteful number, since it uses less digits than its factorization.

638643169 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 615710.

The product of its digits is 559872, while the sum is 46.

The square root of 638643169 is about 25271.3903258210. The cubic root of 638643169 is about 861.1644443483.

The spelling of 638643169 in words is "six hundred thirty-eight million, six hundred forty-three thousand, one hundred sixty-nine".