8172821 has 2 divisors, whose sum is σ = 8172822. Its totient is φ = 8172820.

The previous prime is 8172713. The next prime is 8172833. The reversal of 8172821 is 1282718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5880625 + 2292196 = 2425^2 + 1514^2 .

It is a cyclic number.

It is not a de Polignac number, because 8172821 - 2¹⁴ = 8156437 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8175821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4086410 + 4086411.

It is an arithmetic number, because the mean of its divisors is an integer number (4086411).

Almost surely, 2^8172821 is an apocalyptic number.

It is an amenable number.

8172821 is a deficient number, since it is larger than the sum of its proper divisors (1).

8172821 is an equidigital number, since it uses as much as digits as its factorization.

8172821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1792, while the sum is 29.

The square root of 8172821 is about 2858.8146144862. The cubic root of 8172821 is about 201.4299271767.

The spelling of 8172821 in words is "eight million, one hundred seventy-two thousand, eight hundred twenty-one".