638772161 has 16 divisors (see below), whose sum is σ = 690197760. Its totient is φ = 588994560.

The previous prime is 638772097. The next prime is 638772259. The reversal of 638772161 is 161277836.

It is a cyclic number.

It is not a de Polignac number, because 638772161 - 2⁶ = 638772097 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638772361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 199985 + ... + 203153.

It is an arithmetic number, because the mean of its divisors is an integer number (43137360).

Almost surely, 2^638772161 is an apocalyptic number.

It is an amenable number.

638772161 is a deficient number, since it is larger than the sum of its proper divisors (51425599).

638772161 is a wasteful number, since it uses less digits than its factorization.

638772161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3424.

The product of its digits is 84672, while the sum is 41.

The square root of 638772161 is about 25273.9423319750. The cubic root of 638772161 is about 861.2224192611. Note that the first 3 decimals are identical.

The spelling of 638772161 in words is "six hundred thirty-eight million, seven hundred seventy-two thousand, one hundred sixty-one".