21728269 has 2 divisors, whose sum is σ = 21728270. Its totient is φ = 21728268.

The previous prime is 21728249. The next prime is 21728293. The reversal of 21728269 is 96282712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18966025 + 2762244 = 4355^2 + 1662^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21728269 is a prime.

It is a super-2 number, since 2×21728269² = 944235347472722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21728249) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10864134 + 10864135.

It is an arithmetic number, because the mean of its divisors is an integer number (10864135).

Almost surely, 2^21728269 is an apocalyptic number.

It is an amenable number.

21728269 is a deficient number, since it is larger than the sum of its proper divisors (1).

21728269 is an equidigital number, since it uses as much as digits as its factorization.

21728269 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24192, while the sum is 37.

The square root of 21728269 is about 4661.3591365609. The cubic root of 21728269 is about 279.0455127167.

It can be divided in two parts, 2 and 1728269, that added together give a palindrome (1728271).

The spelling of 21728269 in words is "twenty-one million, seven hundred twenty-eight thousand, two hundred sixty-nine".