21006818 has 32 divisors (see below), whose sum is σ = 38231040. Its totient is φ = 8456400.

The previous prime is 21006803. The next prime is 21006829. The reversal of 21006818 is 81860012.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 39905 + ... + 40427.

It is an arithmetic number, because the mean of its divisors is an integer number (1194720).

Almost surely, 2^21006818 is an apocalyptic number.

21006818 is a deficient number, since it is larger than the sum of its proper divisors (17224222).

21006818 is a wasteful number, since it uses less digits than its factorization.

21006818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 702.

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 21006818 is about 4583.3195393732. The cubic root of 21006818 is about 275.9222720980.

The spelling of 21006818 in words is "twenty-one million, six thousand, eight hundred eighteen".