217979 has 2 divisors, whose sum is σ = 217980. Its totient is φ = 217978.

The previous prime is 217969. The next prime is 217981. The reversal of 217979 is 979712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 217979 - 2¹⁶ = 152443 is a prime.

Together with 217981, it forms a pair of twin primes.

It is a Chen prime.

It is a plaindrome in base 15.

It is not a weakly prime, because it can be changed into another prime (217909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108989 + 108990.

It is an arithmetic number, because the mean of its divisors is an integer number (108990).

2²¹⁷⁹⁷⁹ is an apocalyptic number.

217979 is a deficient number, since it is larger than the sum of its proper divisors (1).

217979 is an equidigital number, since it uses as much as digits as its factorization.

217979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7938, while the sum is 35.

The square root of 217979 is about 466.8822121264. The cubic root of 217979 is about 60.1826839524.

It can be divided in two parts, 21 and 7979, that added together give a cube (8000 = 20³).

The spelling of 217979 in words is "two hundred seventeen thousand, nine hundred seventy-nine".