638161 has 2 divisors, whose sum is σ = 638162. Its totient is φ = 638160.

The previous prime is 638159. The next prime is 638171. The reversal of 638161 is 161836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 342225 + 295936 = 585^2 + 544^2 .

It is a cyclic number.

It is not a de Polignac number, because 638161 - 2¹ = 638159 is a prime.

Together with 638159, it forms a pair of twin primes.

It is an alternating number because its digits alternate between even and odd.

638161 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (638171) 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 as a sum of consecutive naturals, namely, 319080 + 319081.

It is an arithmetic number, because the mean of its divisors is an integer number (319081).

2⁶³⁸¹⁶¹ is an apocalyptic number.

It is an amenable number.

638161 is a deficient number, since it is larger than the sum of its proper divisors (1).

638161 is an equidigital number, since it uses as much as digits as its factorization.

638161 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 25.

The square root of 638161 is about 798.8497981473. The cubic root of 638161 is about 86.0947666362.

Adding to 638161 its reverse (161836), we get a palindrome (799997).

The spelling of 638161 in words is "six hundred thirty-eight thousand, one hundred sixty-one".