208218221 has 4 divisors (see below), whose sum is σ = 211150944. Its totient is φ = 205285500.

The previous prime is 208218209. The next prime is 208218239. The reversal of 208218221 is 122812802.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-208218221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (208218281) 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 in 3 ways as a sum of consecutive naturals, for example, 1466255 + ... + 1466396.

It is an arithmetic number, because the mean of its divisors is an integer number (52787736).

Almost surely, 2^208218221 is an apocalyptic number.

It is an amenable number.

208218221 is a deficient number, since it is larger than the sum of its proper divisors (2932723).

208218221 is an equidigital number, since it uses as much as digits as its factorization.

208218221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2932722.

The product of its (nonzero) digits is 1024, while the sum is 26.

The square root of 208218221 is about 14429.7685705627. The cubic root of 208218221 is about 592.7063460225.

The spelling of 208218221 in words is "two hundred eight million, two hundred eighteen thousand, two hundred twenty-one".