21218803 has 4 divisors (see below), whose sum is σ = 21228480. Its totient is φ = 21209128.

The previous prime is 21218777. The next prime is 21218809. The reversal of 21218803 is 30881212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21218803 is a prime.

It is a Duffinian 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 3 ways as a sum of consecutive naturals, for example, 201 + ... + 6517.

It is an arithmetic number, because the mean of its divisors is an integer number (5307120).

Almost surely, 2^21218803 is an apocalyptic number.

21218803 is a deficient number, since it is larger than the sum of its proper divisors (9677).

21218803 is an equidigital number, since it uses as much as digits as its factorization.

21218803 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9676.

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 21218803 is about 4606.3871960572. The cubic root of 21218803 is about 276.8473007906.

The spelling of 21218803 in words is "twenty-one million, two hundred eighteen thousand, eight hundred three".