42218381 has 2 divisors, whose sum is σ = 42218382. Its totient is φ = 42218380.

The previous prime is 42218359. The next prime is 42218383. The reversal of 42218381 is 18381224.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 33756100 + 8462281 = 5810^2 + 2909^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-42218381 is a prime.

It is a super-2 number, since 2×42218381² = 3564783388522322, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 42218383, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42218383) 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, 21109190 + 21109191.

It is an arithmetic number, because the mean of its divisors is an integer number (21109191).

Almost surely, 2^42218381 is an apocalyptic number.

It is an amenable number.

42218381 is a deficient number, since it is larger than the sum of its proper divisors (1).

42218381 is an equidigital number, since it uses as much as digits as its factorization.

42218381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3072, while the sum is 29.

The square root of 42218381 is about 6497.5673140030. The cubic root of 42218381 is about 348.2040821921.

The spelling of 42218381 in words is "forty-two million, two hundred eighteen thousand, three hundred eighty-one".