218112821 has 2 divisors, whose sum is σ = 218112822. Its totient is φ = 218112820.

The previous prime is 218112809. The next prime is 218112827. The reversal of 218112821 is 128211812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 133656721 + 84456100 = 11561^2 + 9190^2 .

It is a cyclic number.

It is not a de Polignac number, because 218112821 - 2⁶ = 218112757 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (218112827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109056410 + 109056411.

It is an arithmetic number, because the mean of its divisors is an integer number (109056411).

Almost surely, 2^218112821 is an apocalyptic number.

It is an amenable number.

218112821 is a deficient number, since it is larger than the sum of its proper divisors (1).

218112821 is an equidigital number, since it uses as much as digits as its factorization.

218112821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 512, while the sum is 26.

The square root of 218112821 is about 14768.6431671972. The cubic root of 218112821 is about 601.9499715603.

The spelling of 218112821 in words is "two hundred eighteen million, one hundred twelve thousand, eight hundred twenty-one".