128646821 has 2 divisors, whose sum is σ = 128646822. Its totient is φ = 128646820.

The previous prime is 128646811. The next prime is 128646857.

It is a happy number.

128646821 is nontrivially palindromic in base 10.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 90516196 + 38130625 = 9514^2 + 6175^2 .

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 128646821 - 2¹⁸ = 128384677 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128646811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64323410 + 64323411.

It is an arithmetic number, because the mean of its divisors is an integer number (64323411).

Almost surely, 2^128646821 is an apocalyptic number.

It is an amenable number.

128646821 is a deficient number, since it is larger than the sum of its proper divisors (1).

128646821 is an equidigital number, since it uses as much as digits as its factorization.

128646821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36864, while the sum is 38.

The square root of 128646821 is about 11342.2581966732. The cubic root of 128646821 is about 504.8158934156.

The spelling of 128646821 in words is "one hundred twenty-eight million, six hundred forty-six thousand, eight hundred twenty-one".