217216121 has 2 divisors, whose sum is σ = 217216122. Its totient is φ = 217216120.

The previous prime is 217216081. The next prime is 217216133. The reversal of 217216121 is 121612712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 215355625 + 1860496 = 14675^2 + 1364^2 .

It is a cyclic number.

It is not a de Polignac number, because 217216121 - 2²² = 213021817 is a prime.

It is not a weakly prime, because it can be changed into another prime (217216421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108608060 + 108608061.

It is an arithmetic number, because the mean of its divisors is an integer number (108608061).

Almost surely, 2^217216121 is an apocalyptic number.

It is an amenable number.

217216121 is a deficient number, since it is larger than the sum of its proper divisors (1).

217216121 is an equidigital number, since it uses as much as digits as its factorization.

217216121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 336, while the sum is 23.

The square root of 217216121 is about 14738.2536618149. The cubic root of 217216121 is about 601.1239312792.

Adding to 217216121 its reverse (121612712), we get a palindrome (338828833).

The spelling of 217216121 in words is "two hundred seventeen million, two hundred sixteen thousand, one hundred twenty-one".