42181 has 2 divisors, whose sum is σ = 42182. Its totient is φ = 42180.

The previous prime is 42179. The next prime is 42187. The reversal of 42181 is 18124.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 25281 + 16900 = 159^2 + 130^2 .

It is a cyclic number.

It is not a de Polignac number, because 42181 - 2¹ = 42179 is a prime.

It is a super-2 number, since 2×42181² = 3558473522, which contains 22 as substring.

Together with 42179, it forms a pair of twin primes.

It is a nialpdrome in base 15.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42187) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21090 + 21091.

It is an arithmetic number, because the mean of its divisors is an integer number (21091).

2⁴²¹⁸¹ is an apocalyptic number.

It is an amenable number.

42181 is a deficient number, since it is larger than the sum of its proper divisors (1).

42181 is an equidigital number, since it uses as much as digits as its factorization.

42181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 64, while the sum is 16.

The square root of 42181 is about 205.3801353588. The cubic root of 42181 is about 34.8101282890.

The spelling of 42181 in words is "forty-two thousand, one hundred eighty-one".