208128121 has 2 divisors, whose sum is σ = 208128122. Its totient is φ = 208128120.

The previous prime is 208128097. The next prime is 208128143. The reversal of 208128121 is 121821802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 206066025 + 2062096 = 14355^2 + 1436^2 .

It is a cyclic number.

It is not a de Polignac number, because 208128121 - 2⁷ = 208127993 is a prime.

It is not a weakly prime, because it can be changed into another prime (208128181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104064060 + 104064061.

It is an arithmetic number, because the mean of its divisors is an integer number (104064061).

Almost surely, 2^208128121 is an apocalyptic number.

It is an amenable number.

208128121 is a deficient number, since it is larger than the sum of its proper divisors (1).

208128121 is an equidigital number, since it uses as much as digits as its factorization.

208128121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 512, while the sum is 25.

The square root of 208128121 is about 14426.6462145573. The cubic root of 208128121 is about 592.6208419038.

Adding to 208128121 its reverse (121821802), we get a palindrome (329949923).

The spelling of 208128121 in words is "two hundred eight million, one hundred twenty-eight thousand, one hundred twenty-one".