212817221 has 2 divisors, whose sum is σ = 212817222. Its totient is φ = 212817220.

The previous prime is 212817197. The next prime is 212817239. The reversal of 212817221 is 122718212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 131997121 + 80820100 = 11489^2 + 8990^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-212817221 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 (212817421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 106408610 + 106408611.

It is an arithmetic number, because the mean of its divisors is an integer number (106408611).

Almost surely, 2^212817221 is an apocalyptic number.

It is an amenable number.

212817221 is a deficient number, since it is larger than the sum of its proper divisors (1).

212817221 is an equidigital number, since it uses as much as digits as its factorization.

212817221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 896, while the sum is 26.

The square root of 212817221 is about 14588.2562700276. The cubic root of 212817221 is about 597.0383878827.

Subtracting from 212817221 its reverse (122718212), we obtain a palindrome (90099009).

The spelling of 212817221 in words is "two hundred twelve million, eight hundred seventeen thousand, two hundred twenty-one".