16808821 has 2 divisors, whose sum is σ = 16808822. Its totient is φ = 16808820.

The previous prime is 16808819. The next prime is 16808833. The reversal of 16808821 is 12880861.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15295921 + 1512900 = 3911^2 + 1230^2 .

It is a cyclic number.

It is not a de Polignac number, because 16808821 - 2¹ = 16808819 is a prime.

Together with 16808819, it forms a pair of twin primes.

It is equal to p_1079773 and since 16808821 and 1079773 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 (16808881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8404410 + 8404411.

It is an arithmetic number, because the mean of its divisors is an integer number (8404411).

Almost surely, 2^16808821 is an apocalyptic number.

It is an amenable number.

16808821 is a deficient number, since it is larger than the sum of its proper divisors (1).

16808821 is an equidigital number, since it uses as much as digits as its factorization.

16808821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6144, while the sum is 34.

The square root of 16808821 is about 4099.8562169910. The cubic root of 16808821 is about 256.1606505069.

It can be divided in two parts, 1680 and 8821, that added together give a palindrome (10501).

The spelling of 16808821 in words is "sixteen million, eight hundred eight thousand, eight hundred twenty-one".