217428121 has 2 divisors, whose sum is σ = 217428122. Its totient is φ = 217428120.

The previous prime is 217428089. The next prime is 217428139. The reversal of 217428121 is 121824712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 208398096 + 9030025 = 14436^2 + 3005^2 .

It is a cyclic number.

It is not a de Polignac number, because 217428121 - 2⁵ = 217428089 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 217428121.

It is not a weakly prime, because it can be changed into another prime (217428151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108714060 + 108714061.

It is an arithmetic number, because the mean of its divisors is an integer number (108714061).

Almost surely, 2^217428121 is an apocalyptic number.

It is an amenable number.

217428121 is a deficient number, since it is larger than the sum of its proper divisors (1).

217428121 is an equidigital number, since it uses as much as digits as its factorization.

217428121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1792, while the sum is 28.

The square root of 217428121 is about 14745.4440760528. Note that the first 3 decimals coincide. The cubic root of 217428121 is about 601.3194306371.

The spelling of 217428121 in words is "two hundred seventeen million, four hundred twenty-eight thousand, one hundred twenty-one".