21811771 has 2 divisors, whose sum is σ = 21811772. Its totient is φ = 21811770.

The previous prime is 21811747. The next prime is 21811813. The reversal of 21811771 is 17711812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21811771 - 2⁵ = 21811739 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21811721) 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, 10905885 + 10905886.

It is an arithmetic number, because the mean of its divisors is an integer number (10905886).

Almost surely, 2^21811771 is an apocalyptic number.

21811771 is a deficient number, since it is larger than the sum of its proper divisors (1).

21811771 is an equidigital number, since it uses as much as digits as its factorization.

21811771 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 784, while the sum is 28.

The square root of 21811771 is about 4670.3073774646. The cubic root of 21811771 is about 279.4025142105.

The spelling of 21811771 in words is "twenty-one million, eight hundred eleven thousand, seven hundred seventy-one".