21221218 has 8 divisors (see below), whose sum is σ = 32016348. Its totient is φ = 10549104.

The previous prime is 21221171. The next prime is 21221237. The reversal of 21221218 is 81212212.

It can be written as a sum of positive squares in 2 ways, for example, as 15233409 + 5987809 = 3903^2 + 2447^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a junction number, because it is equal to n+sod(n) for n = 21221195 and 21221204.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30321 + ... + 31012.

Almost surely, 2^21221218 is an apocalyptic number.

21221218 is a deficient number, since it is larger than the sum of its proper divisors (10795130).

21221218 is a wasteful number, since it uses less digits than its factorization.

21221218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61508.

The product of its digits is 128, while the sum is 19.

The square root of 21221218 is about 4606.6493246176. The cubic root of 21221218 is about 276.8578034388.

The spelling of 21221218 in words is "twenty-one million, two hundred twenty-one thousand, two hundred eighteen".