643251221 has 2 divisors, whose sum is σ = 643251222. Its totient is φ = 643251220.

The previous prime is 643251187. The next prime is 643251241. The reversal of 643251221 is 122152346.

It is a happy number.

643251221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 600936196 + 42315025 = 24514^2 + 6505^2 .

It is a cyclic number.

It is not a de Polignac number, because 643251221 - 2⁶ = 643251157 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 (643251241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321625610 + 321625611.

It is an arithmetic number, because the mean of its divisors is an integer number (321625611).

Almost surely, 2^643251221 is an apocalyptic number.

It is an amenable number.

643251221 is a deficient number, since it is larger than the sum of its proper divisors (1).

643251221 is an equidigital number, since it uses as much as digits as its factorization.

643251221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2880, while the sum is 26.

The square root of 643251221 is about 25362.3977770242. The cubic root of 643251221 is about 863.2306917557.

The spelling of 643251221 in words is "six hundred forty-three million, two hundred fifty-one thousand, two hundred twenty-one".