21003811 has 2 divisors, whose sum is σ = 21003812. Its totient is φ = 21003810.

The previous prime is 21003803. The next prime is 21003821. The reversal of 21003811 is 11830012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21003811 - 2³ = 21003803 is a prime.

It is not a weakly prime, because it can be changed into another prime (21003821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501905 + 10501906.

It is an arithmetic number, because the mean of its divisors is an integer number (10501906).

Almost surely, 2^21003811 is an apocalyptic number.

21003811 is a deficient number, since it is larger than the sum of its proper divisors (1).

21003811 is an equidigital number, since it uses as much as digits as its factorization.

21003811 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 16.

The square root of 21003811 is about 4582.9914902823. The cubic root of 21003811 is about 275.9091059303.

Adding to 21003811 its reverse (11830012), we get a palindrome (32833823).

The spelling of 21003811 in words is "twenty-one million, three thousand, eight hundred eleven".