208138321 has 2 divisors, whose sum is σ = 208138322. Its totient is φ = 208138320.

The previous prime is 208138319. The next prime is 208138349. The reversal of 208138321 is 123831802.

208138321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an a-pointer prime, because the next prime (208138349) can be obtained adding 208138321 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 205779025 + 2359296 = 14345^2 + 1536^2 .

It is a cyclic number.

It is not a de Polignac number, because 208138321 - 2¹ = 208138319 is a prime.

Together with 208138319, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 208138321.

It is not a weakly prime, because it can be changed into another prime (208138351) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104069160 + 104069161.

It is an arithmetic number, because the mean of its divisors is an integer number (104069161).

Almost surely, 2^208138321 is an apocalyptic number.

It is an amenable number.

208138321 is a deficient number, since it is larger than the sum of its proper divisors (1).

208138321 is an equidigital number, since it uses as much as digits as its factorization.

208138321 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 208138321 is about 14426.9997227421. Note that the first 3 decimals coincide. The cubic root of 208138321 is about 592.6305228539.

The spelling of 208138321 in words is "two hundred eight million, one hundred thirty-eight thousand, three hundred twenty-one".