212661221 has 2 divisors, whose sum is σ = 212661222. Its totient is φ = 212661220.

The previous prime is 212661181. The next prime is 212661227. The reversal of 212661221 is 122166212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 207648100 + 5013121 = 14410^2 + 2239^2 .

It is a cyclic number.

It is not a de Polignac number, because 212661221 - 2¹⁰ = 212660197 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 (212661227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 106330610 + 106330611.

It is an arithmetic number, because the mean of its divisors is an integer number (106330611).

Almost surely, 2^212661221 is an apocalyptic number.

It is an amenable number.

212661221 is a deficient number, since it is larger than the sum of its proper divisors (1).

212661221 is an equidigital number, since it uses as much as digits as its factorization.

212661221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 576, while the sum is 23.

The square root of 212661221 is about 14582.9085233365. The cubic root of 212661221 is about 596.8924711898.

The spelling of 212661221 in words is "two hundred twelve million, six hundred sixty-one thousand, two hundred twenty-one".