21218056 has 16 divisors (see below), whose sum is σ = 40631040. Its totient is φ = 10383120.

The previous prime is 21218011. The next prime is 21218059. The reversal of 21218056 is 65081212.

It is a self number, because there is not a number n which added to its sum of digits gives 21218056.

It is not an unprimeable number, because it can be changed into a prime (21218059) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27840 + ... + 28591.

It is an arithmetic number, because the mean of its divisors is an integer number (2539440).

Almost surely, 2^21218056 is an apocalyptic number.

It is an amenable number.

21218056 is a deficient number, since it is larger than the sum of its proper divisors (19412984).

21218056 is a wasteful number, since it uses less digits than its factorization.

21218056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56484 (or 56480 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 21218056 is about 4606.3061122770. The cubic root of 21218056 is about 276.8440519840.

Adding to 21218056 its reverse (65081212), we get a palindrome (86299268).

The spelling of 21218056 in words is "twenty-one million, two hundred eighteen thousand, fifty-six".