21021018 has 8 divisors (see below), whose sum is σ = 42042048. Its totient is φ = 7007004.

The previous prime is 21021001. The next prime is 21021043. The reversal of 21021018 is 81012012.

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

21021018 is an admirable number.

It is a junction number, because it is equal to n+sod(n) for n = 21020988 and 21021006.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1751746 + ... + 1751757.

It is an arithmetic number, because the mean of its divisors is an integer number (5255256).

Almost surely, 2^21021018 is an apocalyptic number.

21021018 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21021018 is a wasteful number, since it uses less digits than its factorization.

21021018 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3503508.

The product of its (nonzero) digits is 32, while the sum is 15.

The square root of 21021018 is about 4584.8683732469. The cubic root of 21021018 is about 275.9844299135.

The spelling of 21021018 in words is "twenty-one million, twenty-one thousand, eighteen".