217640123 has 2 divisors, whose sum is σ = 217640124. Its totient is φ = 217640122.

The previous prime is 217640081. The next prime is 217640149. The reversal of 217640123 is 321046712.

It is an a-pointer prime, because the next prime (217640149) can be obtained adding 217640123 to its sum of digits (26).

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 217640123 - 2²⁰ = 216591547 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 217640092 and 217640101.

It is not a weakly prime, because it can be changed into another prime (217640173) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108820061 + 108820062.

It is an arithmetic number, because the mean of its divisors is an integer number (108820062).

Almost surely, 2^217640123 is an apocalyptic number.

217640123 is a deficient number, since it is larger than the sum of its proper divisors (1).

217640123 is an equidigital number, since it uses as much as digits as its factorization.

217640123 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 26.

The square root of 217640123 is about 14752.6310534765. The cubic root of 217640123 is about 601.5148047997.

Adding to 217640123 its reverse (321046712), we get a palindrome (538686835).

The spelling of 217640123 in words is "two hundred seventeen million, six hundred forty thousand, one hundred twenty-three".