21005219 has 2 divisors, whose sum is σ = 21005220. Its totient is φ = 21005218.

The previous prime is 21005209. The next prime is 21005227. The reversal of 21005219 is 91250012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21005219 is a prime.

It is a super-2 number, since 2×21005219² = 882438450475922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21005219.

It is not a weakly prime, because it can be changed into another prime (21005209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502609 + 10502610.

It is an arithmetic number, because the mean of its divisors is an integer number (10502610).

Almost surely, 2^21005219 is an apocalyptic number.

21005219 is a deficient number, since it is larger than the sum of its proper divisors (1).

21005219 is an equidigital number, since it uses as much as digits as its factorization.

21005219 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 180, while the sum is 20.

The square root of 21005219 is about 4583.1450991650. The cubic root of 21005219 is about 275.9152710232.

The spelling of 21005219 in words is "twenty-one million, five thousand, two hundred nineteen".