7218221 has 2 divisors, whose sum is σ = 7218222. Its totient is φ = 7218220.

The previous prime is 7218209. The next prime is 7218227. The reversal of 7218221 is 1228127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5692996 + 1525225 = 2386^2 + 1235^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7218221 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7218227) 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, 3609110 + 3609111.

It is an arithmetic number, because the mean of its divisors is an integer number (3609111).

Almost surely, 2^7218221 is an apocalyptic number.

It is an amenable number.

7218221 is a deficient number, since it is larger than the sum of its proper divisors (1).

7218221 is an equidigital number, since it uses as much as digits as its factorization.

7218221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 448, while the sum is 23.

The square root of 7218221 is about 2686.6747104925. The cubic root of 7218221 is about 193.2606302800.

The spelling of 7218221 in words is "seven million, two hundred eighteen thousand, two hundred twenty-one".