128778217 has 2 divisors, whose sum is σ = 128778218. Its totient is φ = 128778216.

The previous prime is 128778203. The next prime is 128778227. The reversal of 128778217 is 712877821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 107765161 + 21013056 = 10381^2 + 4584^2 .

It is an emirp because it is prime and its reverse (712877821) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 128778217 - 2²³ = 120389609 is a prime.

It is not a weakly prime, because it can be changed into another prime (128778227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64389108 + 64389109.

It is an arithmetic number, because the mean of its divisors is an integer number (64389109).

Almost surely, 2^128778217 is an apocalyptic number.

It is an amenable number.

128778217 is a deficient number, since it is larger than the sum of its proper divisors (1).

128778217 is an equidigital number, since it uses as much as digits as its factorization.

128778217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 87808, while the sum is 43.

The square root of 128778217 is about 11348.0490393724. The cubic root of 128778217 is about 504.9877028669.

The spelling of 128778217 in words is "one hundred twenty-eight million, seven hundred seventy-eight thousand, two hundred seventeen".