21928169 has 2 divisors, whose sum is σ = 21928170. Its totient is φ = 21928168.

The previous prime is 21928133. The next prime is 21928171. The reversal of 21928169 is 96182912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20070400 + 1857769 = 4480^2 + 1363^2 .

It is a cyclic number.

It is not a de Polignac number, because 21928169 - 2¹² = 21924073 is a prime.

It is a super-2 number, since 2×21928169² = 961689191385122, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 21928171, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21928189) 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, 10964084 + 10964085.

It is an arithmetic number, because the mean of its divisors is an integer number (10964085).

Almost surely, 2^21928169 is an apocalyptic number.

It is an amenable number.

21928169 is a deficient number, since it is larger than the sum of its proper divisors (1).

21928169 is an equidigital number, since it uses as much as digits as its factorization.

21928169 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 38.

The square root of 21928169 is about 4682.7522889856. The cubic root of 21928169 is about 279.8986410339.

The spelling of 21928169 in words is "twenty-one million, nine hundred twenty-eight thousand, one hundred sixty-nine".