21305056 has 12 divisors (see below), whose sum is σ = 41944392. Its totient is φ = 10652512.

The previous prime is 21305047. The next prime is 21305059. The reversal of 21305056 is 65050312.

It is a happy number.

It is a super-2 number, since 2×21305056² = 907810822326272, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305059) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332860 + ... + 332923.

It is an arithmetic number, because the mean of its divisors is an integer number (3495366).

Almost surely, 2^21305056 is an apocalyptic number.

It is an amenable number.

21305056 is a deficient number, since it is larger than the sum of its proper divisors (20639336).

21305056 is an equidigital number, since it uses as much as digits as its factorization.

21305056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 665793 (or 665785 counting only the distinct ones).

The product of its (nonzero) digits is 900, while the sum is 22.

The square root of 21305056 is about 4615.7400273412. The cubic root of 21305056 is about 277.2219155089.

Adding to 21305056 its reverse (65050312), we get a palindrome (86355368).

The spelling of 21305056 in words is "twenty-one million, three hundred five thousand, fifty-six".