638210161 has 4 divisors (see below), whose sum is σ = 638321652. Its totient is φ = 638098672.

The previous prime is 638210143. The next prime is 638210191. The reversal of 638210161 is 161012836.

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

It can be written as a sum of positive squares in 2 ways, for example, as 34574400 + 603635761 = 5880^2 + 24569^2 .

It is a cyclic number.

It is not a de Polignac number, because 638210161 - 2⁵ = 638210129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638210191) 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 3 ways as a sum of consecutive naturals, for example, 46666 + ... + 58771.

It is an arithmetic number, because the mean of its divisors is an integer number (159580413).

Almost surely, 2^638210161 is an apocalyptic number.

It is an amenable number.

638210161 is a deficient number, since it is larger than the sum of its proper divisors (111491).

638210161 is a wasteful number, since it uses less digits than its factorization.

638210161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111490.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 638210161 is about 25262.8217149233. The cubic root of 638210161 is about 860.9697736159.

Adding to 638210161 its reverse (161012836), we get a palindrome (799222997).

The spelling of 638210161 in words is "six hundred thirty-eight million, two hundred ten thousand, one hundred sixty-one".