21909863 has 2 divisors, whose sum is σ = 21909864. Its totient is φ = 21909862.

The previous prime is 21909859. The next prime is 21909887. The reversal of 21909863 is 36890912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21909863 - 2² = 21909859 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21909163) 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, 10954931 + 10954932.

It is an arithmetic number, because the mean of its divisors is an integer number (10954932).

Almost surely, 2^21909863 is an apocalyptic number.

21909863 is a deficient number, since it is larger than the sum of its proper divisors (1).

21909863 is an equidigital number, since it uses as much as digits as its factorization.

21909863 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 21909863 is about 4680.7972611511. The cubic root of 21909863 is about 279.8207313370.

The spelling of 21909863 in words is "twenty-one million, nine hundred nine thousand, eight hundred sixty-three".