21105569 has 2 divisors, whose sum is σ = 21105570. Its totient is φ = 21105568.

The previous prime is 21105563. The next prime is 21105571. The reversal of 21105569 is 96550112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18593344 + 2512225 = 4312^2 + 1585^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21105569 is a prime.

It is a super-2 number, since 2×21105569² = 890890085627522, which contains 22 as substring.

Together with 21105571, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21105563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552784 + 10552785.

It is an arithmetic number, because the mean of its divisors is an integer number (10552785).

Almost surely, 2^21105569 is an apocalyptic number.

It is an amenable number.

21105569 is a deficient number, since it is larger than the sum of its proper divisors (1).

21105569 is an equidigital number, since it uses as much as digits as its factorization.

21105569 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2700, while the sum is 29.

The square root of 21105569 is about 4594.0797772786. The cubic root of 21105569 is about 276.3539575845.

The spelling of 21105569 in words is "twenty-one million, one hundred five thousand, five hundred sixty-nine".