221909213 has 2 divisors, whose sum is σ = 221909214. Its totient is φ = 221909212.

The previous prime is 221909209. The next prime is 221909243. The reversal of 221909213 is 312909122.

221909213 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 175642009 + 46267204 = 13253^2 + 6802^2 .

It is a cyclic number.

It is not a de Polignac number, because 221909213 - 2² = 221909209 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221909243) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110954606 + 110954607.

It is an arithmetic number, because the mean of its divisors is an integer number (110954607).

Almost surely, 2^221909213 is an apocalyptic number.

It is an amenable number.

221909213 is a deficient number, since it is larger than the sum of its proper divisors (1).

221909213 is an equidigital number, since it uses as much as digits as its factorization.

221909213 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 221909213 is about 14896.6175019700. The cubic root of 221909213 is about 605.4223428971.

Subtracting 221909213 from its reverse (312909122), we obtain a palindrome (90999909).

The spelling of 221909213 in words is "two hundred twenty-one million, nine hundred nine thousand, two hundred thirteen".