218211997 has 2 divisors, whose sum is σ = 218211998. Its totient is φ = 218211996.

The previous prime is 218211947. The next prime is 218212003. The reversal of 218211997 is 799112812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 218034756 + 177241 = 14766^2 + 421^2 .

It is a cyclic number.

It is not a de Polignac number, because 218211997 - 2⁷ = 218211869 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (218211907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109105998 + 109105999.

It is an arithmetic number, because the mean of its divisors is an integer number (109105999).

Almost surely, 2^218211997 is an apocalyptic number.

It is an amenable number.

218211997 is a deficient number, since it is larger than the sum of its proper divisors (1).

218211997 is an equidigital number, since it uses as much as digits as its factorization.

218211997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18144, while the sum is 40.

The square root of 218211997 is about 14772.0004400217. Note that the first 3 decimals coincide. The cubic root of 218211997 is about 602.0411933784.

The spelling of 218211997 in words is "two hundred eighteen million, two hundred eleven thousand, nine hundred ninety-seven".