643221217 has 2 divisors, whose sum is σ = 643221218. Its totient is φ = 643221216.

The previous prime is 643221211. The next prime is 643221223. The reversal of 643221217 is 712122346.

643221217 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a balanced prime because it is at equal distance from previous prime (643221211) and next prime (643221223).

It can be written as a sum of positive squares in only one way, i.e., 429359841 + 213861376 = 20721^2 + 14624^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643221217 is a prime.

It is a super-2 number, since 2×643221217² = 827467067997922178, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (643221211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321610608 + 321610609.

It is an arithmetic number, because the mean of its divisors is an integer number (321610609).

Almost surely, 2^643221217 is an apocalyptic number.

It is an amenable number.

643221217 is a deficient number, since it is larger than the sum of its proper divisors (1).

643221217 is an equidigital number, since it uses as much as digits as its factorization.

643221217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4032, while the sum is 28.

The square root of 643221217 is about 25361.8062645388. The cubic root of 643221217 is about 863.2172699512.

The spelling of 643221217 in words is "six hundred forty-three million, two hundred twenty-one thousand, two hundred seventeen".