20004821 has 2 divisors, whose sum is σ = 20004822. Its totient is φ = 20004820.

The previous prime is 20004811. The next prime is 20004823. The reversal of 20004821 is 12840002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15295921 + 4708900 = 3911^2 + 2170^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20004821 is a prime.

Together with 20004823, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20004821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20004823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10002410 + 10002411.

It is an arithmetic number, because the mean of its divisors is an integer number (10002411).

Almost surely, 2^20004821 is an apocalyptic number.

It is an amenable number.

20004821 is a deficient number, since it is larger than the sum of its proper divisors (1).

20004821 is an equidigital number, since it uses as much as digits as its factorization.

20004821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 20004821 is about 4472.6749267077. The cubic root of 20004821 is about 271.4635702528.

Adding to 20004821 its reverse (12840002), we get a palindrome (32844823).

The spelling of 20004821 in words is "twenty million, four thousand, eight hundred twenty-one".