217564849 has 2 divisors, whose sum is σ = 217564850. Its totient is φ = 217564848.

The previous prime is 217564817. The next prime is 217564859. The reversal of 217564849 is 948465712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 179372449 + 38192400 = 13393^2 + 6180^2 .

It is a cyclic number.

It is not a de Polignac number, because 217564849 - 2⁵ = 217564817 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 217564799 and 217564808.

It is not a weakly prime, because it can be changed into another prime (217564859) 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, 108782424 + 108782425.

It is an arithmetic number, because the mean of its divisors is an integer number (108782425).

Almost surely, 2^217564849 is an apocalyptic number.

It is an amenable number.

217564849 is a deficient number, since it is larger than the sum of its proper divisors (1).

217564849 is an equidigital number, since it uses as much as digits as its factorization.

217564849 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 483840, while the sum is 46.

The square root of 217564849 is about 14750.0796269037. The cubic root of 217564849 is about 601.4454492570.

The spelling of 217564849 in words is "two hundred seventeen million, five hundred sixty-four thousand, eight hundred forty-nine".