21771811 has 2 divisors, whose sum is σ = 21771812. Its totient is φ = 21771810.

The previous prime is 21771809. The next prime is 21771833. The reversal of 21771811 is 11817712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21771811 - 2¹ = 21771809 is a prime.

Together with 21771809, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21771811.

It is not a weakly prime, because it can be changed into another prime (21771311) 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, 10885905 + 10885906.

It is an arithmetic number, because the mean of its divisors is an integer number (10885906).

Almost surely, 2^21771811 is an apocalyptic number.

21771811 is a deficient number, since it is larger than the sum of its proper divisors (1).

21771811 is an equidigital number, since it uses as much as digits as its factorization.

21771811 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 21771811 is about 4666.0273252522. The cubic root of 21771811 is about 279.2317845373.

The spelling of 21771811 in words is "twenty-one million, seven hundred seventy-one thousand, eight hundred eleven".