128121869 has 2 divisors, whose sum is σ = 128121870. Its totient is φ = 128121868.

The previous prime is 128121821. The next prime is 128121881. The reversal of 128121869 is 968121821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 122655625 + 5466244 = 11075^2 + 2338^2 .

It is an emirp because it is prime and its reverse (968121821) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 128121869 - 2⁸ = 128121613 is a prime.

It is a super-2 number, since 2×128121869² = 32830426632106322, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128021869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64060934 + 64060935.

It is an arithmetic number, because the mean of its divisors is an integer number (64060935).

Almost surely, 2^128121869 is an apocalyptic number.

It is an amenable number.

128121869 is a deficient number, since it is larger than the sum of its proper divisors (1).

128121869 is an equidigital number, since it uses as much as digits as its factorization.

128121869 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13824, while the sum is 38.

The square root of 128121869 is about 11319.0931173836. The cubic root of 128121869 is about 504.1283122641.

The spelling of 128121869 in words is "one hundred twenty-eight million, one hundred twenty-one thousand, eight hundred sixty-nine".