21004811 has 2 divisors, whose sum is σ = 21004812. Its totient is φ = 21004810.

The previous prime is 21004807. The next prime is 21004813. The reversal of 21004811 is 11840012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21004811 - 2² = 21004807 is a prime.

Together with 21004813, 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 21004811.

It is not a weakly prime, because it can be changed into another prime (21004813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502405 + 10502406.

It is an arithmetic number, because the mean of its divisors is an integer number (10502406).

Almost surely, 2^21004811 is an apocalyptic number.

21004811 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004811 is an equidigital number, since it uses as much as digits as its factorization.

21004811 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64, while the sum is 17.

The square root of 21004811 is about 4583.1005880299. The cubic root of 21004811 is about 275.9134845758.

Adding to 21004811 its reverse (11840012), we get a palindrome (32844823).

The spelling of 21004811 in words is "twenty-one million, four thousand, eight hundred eleven".