10001821 has 2 divisors, whose sum is σ = 10001822. Its totient is φ = 10001820.

The previous prime is 10001819. The next prime is 10001833. The reversal of 10001821 is 12810001.

10001821 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9765625 + 236196 = 3125^2 + 486^2 .

It is a cyclic number.

It is not a de Polignac number, because 10001821 - 2¹ = 10001819 is a prime.

Together with 10001819, 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 (10001801) 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, 5000910 + 5000911.

It is an arithmetic number, because the mean of its divisors is an integer number (5000911).

Almost surely, 2^10001821 is an apocalyptic number.

It is an amenable number.

10001821 is a deficient number, since it is larger than the sum of its proper divisors (1).

10001821 is an equidigital number, since it uses as much as digits as its factorization.

10001821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16, while the sum is 13.

The square root of 10001821 is about 3162.5655724427. The cubic root of 10001821 is about 215.4565456280.

Adding to 10001821 its reverse (12810001), we get a palindrome (22811822).

The spelling of 10001821 in words is "ten million, one thousand, eight hundred twenty-one".