21020818 has 16 divisors (see below), whose sum is σ = 38808000. Its totient is φ = 8315856.

The previous prime is 21020803. The next prime is 21020819. The reversal of 21020818 is 81802012.

It is not an unprimeable number, because it can be changed into a prime (21020819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 57568 + ... + 57931.

It is an arithmetic number, because the mean of its divisors is an integer number (2425500).

Almost surely, 2^21020818 is an apocalyptic number.

21020818 is a deficient number, since it is larger than the sum of its proper divisors (17787182).

21020818 is a wasteful number, since it uses less digits than its factorization.

21020818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115521.

The product of its (nonzero) digits is 256, while the sum is 22.

The square root of 21020818 is about 4584.8465623181. The cubic root of 21020818 is about 275.9835546457.

The spelling of 21020818 in words is "twenty-one million, twenty thousand, eight hundred eighteen".