21451811 has 2 divisors, whose sum is σ = 21451812. Its totient is φ = 21451810.

The previous prime is 21451789. The next prime is 21451813. The reversal of 21451811 is 11815412.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21451811 is a prime.

Together with 21451813, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21451813) 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, 10725905 + 10725906.

It is an arithmetic number, because the mean of its divisors is an integer number (10725906).

Almost surely, 2^21451811 is an apocalyptic number.

21451811 is a deficient number, since it is larger than the sum of its proper divisors (1).

21451811 is an equidigital number, since it uses as much as digits as its factorization.

21451811 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 320, while the sum is 23.

The square root of 21451811 is about 4631.6099792621. The cubic root of 21451811 is about 277.8569861168.

It can be divided in two parts, 214 and 51811, that added together give a palindrome (52025).

The spelling of 21451811 in words is "twenty-one million, four hundred fifty-one thousand, eight hundred eleven".