218888921 has 2 divisors, whose sum is σ = 218888922. Its totient is φ = 218888920.

The previous prime is 218888899. The next prime is 218888927. The reversal of 218888921 is 129888812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 177928921 + 40960000 = 13339^2 + 6400^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-218888921 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (218888927) 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, 109444460 + 109444461.

It is an arithmetic number, because the mean of its divisors is an integer number (109444461).

Almost surely, 2^218888921 is an apocalyptic number.

It is an amenable number.

218888921 is a deficient number, since it is larger than the sum of its proper divisors (1).

218888921 is an equidigital number, since it uses as much as digits as its factorization.

218888921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 147456, while the sum is 47.

The square root of 218888921 is about 14794.8950993240. The cubic root of 218888921 is about 602.6630892898.

The spelling of 218888921 in words is "two hundred eighteen million, eight hundred eighty-eight thousand, nine hundred twenty-one".