42581221 has 2 divisors, whose sum is σ = 42581222. Its totient is φ = 42581220.

The previous prime is 42581219. The next prime is 42581267. The reversal of 42581221 is 12218524.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 41796225 + 784996 = 6465^2 + 886^2 .

It is a cyclic number.

It is not a de Polignac number, because 42581221 - 2¹ = 42581219 is a prime.

Together with 42581219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42581281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21290610 + 21290611.

It is an arithmetic number, because the mean of its divisors is an integer number (21290611).

Almost surely, 2^42581221 is an apocalyptic number.

It is an amenable number.

42581221 is a deficient number, since it is larger than the sum of its proper divisors (1).

42581221 is an equidigital number, since it uses as much as digits as its factorization.

42581221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1280, while the sum is 25.

The square root of 42581221 is about 6525.4287981710. The cubic root of 42581221 is about 349.1987685550.

Adding to 42581221 its reverse (12218524), we get a palindrome (54799745).

The spelling of 42581221 in words is "forty-two million, five hundred eighty-one thousand, two hundred twenty-one".