217540243 has 2 divisors, whose sum is σ = 217540244. Its totient is φ = 217540242.

The previous prime is 217540231. The next prime is 217540247. The reversal of 217540243 is 342045712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 217540243 - 2⁹ = 217539731 is a prime.

It is not a weakly prime, because it can be changed into another prime (217540247) 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, 108770121 + 108770122.

It is an arithmetic number, because the mean of its divisors is an integer number (108770122).

Almost surely, 2^217540243 is an apocalyptic number.

217540243 is a deficient number, since it is larger than the sum of its proper divisors (1).

217540243 is an equidigital number, since it uses as much as digits as its factorization.

217540243 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6720, while the sum is 28.

The square root of 217540243 is about 14749.2455061267. The cubic root of 217540243 is about 601.4227744473.

Adding to 217540243 its reverse (342045712), we get a palindrome (559585955).

The spelling of 217540243 in words is "two hundred seventeen million, five hundred forty thousand, two hundred forty-three".