1638181 has 4 divisors (see below), whose sum is σ = 1694700. Its totient is φ = 1581664.

The previous prime is 1638167. The next prime is 1638191. The reversal of 1638181 is 1818361.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1818361 = 307 ⋅5923.

It can be written as a sum of positive squares in 2 ways, for example, as 656100 + 982081 = 810^2 + 991^2 .

It is a cyclic number.

It is not a de Polignac number, because 1638181 - 2⁵ = 1638149 is a prime.

It is a super-2 number, since 2×1638181² = 5367273977522, which contains 22 as substring.

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

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638121) 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 3 ways as a sum of consecutive naturals, for example, 28216 + ... + 28273.

It is an arithmetic number, because the mean of its divisors is an integer number (423675).

2^1638181 is an apocalyptic number.

It is an amenable number.

1638181 is a deficient number, since it is larger than the sum of its proper divisors (56519).

1638181 is an equidigital number, since it uses as much as digits as its factorization.

1638181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56518.

The product of its digits is 1152, while the sum is 28.

The square root of 1638181 is about 1279.9144502661. The cubic root of 1638181 is about 117.8837550994.

The spelling of 1638181 in words is "one million, six hundred thirty-eight thousand, one hundred eighty-one".