217910989 has 2 divisors, whose sum is σ = 217910990. Its totient is φ = 217910988.

The previous prime is 217910933. The next prime is 217911007. The reversal of 217910989 is 989019712.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 170093764 + 47817225 = 13042^2 + 6915^2 .

It is a cyclic number.

It is not a de Polignac number, because 217910989 - 2¹⁷ = 217779917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (217910909) 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, 108955494 + 108955495.

It is an arithmetic number, because the mean of its divisors is an integer number (108955495).

Almost surely, 2^217910989 is an apocalyptic number.

It is an amenable number.

217910989 is a deficient number, since it is larger than the sum of its proper divisors (1).

217910989 is an equidigital number, since it uses as much as digits as its factorization.

217910989 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 81648, while the sum is 46.

The square root of 217910989 is about 14761.8084596705. The cubic root of 217910989 is about 601.7642415941.

The spelling of 217910989 in words is "two hundred seventeen million, nine hundred ten thousand, nine hundred eighty-nine".