217228321 has 2 divisors, whose sum is σ = 217228322. Its totient is φ = 217228320.

The previous prime is 217228301. The next prime is 217228343. The reversal of 217228321 is 123822712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 113188321 + 104040000 = 10639^2 + 10200^2 .

It is a cyclic number.

It is not a de Polignac number, because 217228321 - 2⁵ = 217228289 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 217228321.

It is not a weakly prime, because it can be changed into another prime (217228301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108614160 + 108614161.

It is an arithmetic number, because the mean of its divisors is an integer number (108614161).

Almost surely, 2^217228321 is an apocalyptic number.

It is an amenable number.

217228321 is a deficient number, since it is larger than the sum of its proper divisors (1).

217228321 is an equidigital number, since it uses as much as digits as its factorization.

217228321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2688, while the sum is 28.

The square root of 217228321 is about 14738.6675449309. The cubic root of 217228321 is about 601.1351851625.

The spelling of 217228321 in words is "two hundred seventeen million, two hundred twenty-eight thousand, three hundred twenty-one".