217889989 has 2 divisors, whose sum is σ = 217889990. Its totient is φ = 217889988.

The previous prime is 217889981. The next prime is 217889999. The reversal of 217889989 is 989988712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 202350625 + 15539364 = 14225^2 + 3942^2 .

It is a cyclic number.

It is not a de Polignac number, because 217889989 - 2³ = 217889981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (217889981) 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, 108944994 + 108944995.

It is an arithmetic number, because the mean of its divisors is an integer number (108944995).

Almost surely, 2^217889989 is an apocalyptic number.

It is an amenable number.

217889989 is a deficient number, since it is larger than the sum of its proper divisors (1).

217889989 is an equidigital number, since it uses as much as digits as its factorization.

217889989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5225472, while the sum is 61.

The square root of 217889989 is about 14761.0971475700. The cubic root of 217889989 is about 601.7449103752.

The spelling of 217889989 in words is "two hundred seventeen million, eight hundred eighty-nine thousand, nine hundred eighty-nine".