21042256 has 20 divisors (see below), whose sum is σ = 40929300. Its totient is φ = 10479872.

The previous prime is 21042251. The next prime is 21042283. The reversal of 21042256 is 65224012.

It can be written as a sum of positive squares in 2 ways, for example, as 7203856 + 13838400 = 2684^2 + 3720^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1860 + ... + 6748.

It is an arithmetic number, because the mean of its divisors is an integer number (2046465).

Almost surely, 2^21042256 is an apocalyptic number.

It is an amenable number.

21042256 is a deficient number, since it is larger than the sum of its proper divisors (19887044).

21042256 is a wasteful number, since it uses less digits than its factorization.

21042256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5166 (or 5160 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 22.

The square root of 21042256 is about 4587.1838855664. The cubic root of 21042256 is about 276.0773430236.

Adding to 21042256 its reverse (65224012), we get a palindrome (86266268).

The spelling of 21042256 in words is "twenty-one million, forty-two thousand, two hundred fifty-six".