642218444221 has 2 divisors, whose sum is σ = 642218444222. Its totient is φ = 642218444220.

The previous prime is 642218444207. The next prime is 642218444233. The reversal of 642218444221 is 122444812246.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 606171244900 + 36047199321 = 778570^2 + 189861^2 .

It is a cyclic number.

It is not a de Polignac number, because 642218444221 - 2⁹ = 642218443709 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642218444201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321109222110 + 321109222111.

It is an arithmetic number, because the mean of its divisors is an integer number (321109222111).

Almost surely, 2^642218444221 is an apocalyptic number.

It is an amenable number.

642218444221 is a deficient number, since it is larger than the sum of its proper divisors (1).

642218444221 is an equidigital number, since it uses as much as digits as its factorization.

642218444221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 196608, while the sum is 40.

The spelling of 642218444221 in words is "six hundred forty-two billion, two hundred eighteen million, four hundred forty-four thousand, two hundred twenty-one".