21206056 has 8 divisors (see below), whose sum is σ = 39761370. Its totient is φ = 10603024.

The previous prime is 21206011. The next prime is 21206117. The reversal of 21206056 is 65060212.

It can be written as a sum of positive squares in only one way, i.e., 17724100 + 3481956 = 4210^2 + 1866^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-2 number, since 2×21206056² = 899393622150272, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1325371 + ... + 1325386.

Almost surely, 2^21206056 is an apocalyptic number.

It is an amenable number.

21206056 is a deficient number, since it is larger than the sum of its proper divisors (18555314).

21206056 is a wasteful number, since it uses less digits than its factorization.

21206056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2650763 (or 2650759 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21206056 is about 4605.0033659054. The cubic root of 21206056 is about 276.7918518657.

Adding to 21206056 its reverse (65060212), we get a palindrome (86266268).

The spelling of 21206056 in words is "twenty-one million, two hundred six thousand, fifty-six".