21909229 has 2 divisors, whose sum is σ = 21909230. Its totient is φ = 21909228.

The previous prime is 21909227. The next prime is 21909247. The reversal of 21909229 is 92290912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19096900 + 2812329 = 4370^2 + 1677^2 .

It is a cyclic number.

It is not a de Polignac number, because 21909229 - 2¹ = 21909227 is a prime.

Together with 21909227, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21909194 and 21909203.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21909227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10954614 + 10954615.

It is an arithmetic number, because the mean of its divisors is an integer number (10954615).

Almost surely, 2^21909229 is an apocalyptic number.

It is an amenable number.

21909229 is a deficient number, since it is larger than the sum of its proper divisors (1).

21909229 is an equidigital number, since it uses as much as digits as its factorization.

21909229 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5832, while the sum is 34.

The square root of 21909229 is about 4680.7295371555. The cubic root of 21909229 is about 279.8180322778.

The spelling of 21909229 in words is "twenty-one million, nine hundred nine thousand, two hundred twenty-nine".