128628221 has 2 divisors, whose sum is σ = 128628222. Its totient is φ = 128628220.

The previous prime is 128628217. The next prime is 128628281. The reversal of 128628221 is 122826821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 104755225 + 23872996 = 10235^2 + 4886^2 .

It is a cyclic number.

It is not a de Polignac number, because 128628221 - 2² = 128628217 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is equal to p_7304666 and since 128628221 and 7304666 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128628211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64314110 + 64314111.

It is an arithmetic number, because the mean of its divisors is an integer number (64314111).

Almost surely, 2^128628221 is an apocalyptic number.

It is an amenable number.

128628221 is a deficient number, since it is larger than the sum of its proper divisors (1).

128628221 is an equidigital number, since it uses as much as digits as its factorization.

128628221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6144, while the sum is 32.

The square root of 128628221 is about 11341.4382244934. The cubic root of 128628221 is about 504.7915631650.

The spelling of 128628221 in words is "one hundred twenty-eight million, six hundred twenty-eight thousand, two hundred twenty-one".