21218806 has 16 divisors (see below), whose sum is σ = 36568224. Its totient is φ = 9045504.

The previous prime is 21218777. The next prime is 21218809. The reversal of 21218806 is 60881212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21218809) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1225 + ... + 6628.

It is an arithmetic number, because the mean of its divisors is an integer number (2285514).

Almost surely, 2^21218806 is an apocalyptic number.

21218806 is a deficient number, since it is larger than the sum of its proper divisors (15349418).

21218806 is a wasteful number, since it uses less digits than its factorization.

21218806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8055.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 21218806 is about 4606.3875216920. The cubic root of 21218806 is about 276.8473138379.

The spelling of 21218806 in words is "twenty-one million, two hundred eighteen thousand, eight hundred six".