3128821 has 2 divisors, whose sum is σ = 3128822. Its totient is φ = 3128820.

The previous prime is 3128819. The next prime is 3128843. The reversal of 3128821 is 1288213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2842596 + 286225 = 1686^2 + 535^2 .

It is an emirp because it is prime and its reverse (1288213) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 3128821 - 2¹ = 3128819 is a prime.

Together with 3128819, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3128891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1564410 + 1564411.

It is an arithmetic number, because the mean of its divisors is an integer number (1564411).

Almost surely, 2^3128821 is an apocalyptic number.

It is an amenable number.

3128821 is a deficient number, since it is larger than the sum of its proper divisors (1).

3128821 is an equidigital number, since it uses as much as digits as its factorization.

3128821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 768, while the sum is 25.

The square root of 3128821 is about 1768.8473648113. The cubic root of 3128821 is about 146.2604502236.

The spelling of 3128821 in words is "three million, one hundred twenty-eight thousand, eight hundred twenty-one".