21218718 has 8 divisors (see below), whose sum is σ = 42437448. Its totient is φ = 7072904.

The previous prime is 21218713. The next prime is 21218741. The reversal of 21218718 is 81781212.

It is a happy number.

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

21218718 is an admirable number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21218713) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1768221 + ... + 1768232.

It is an arithmetic number, because the mean of its divisors is an integer number (5304681).

Almost surely, 2^21218718 is an apocalyptic number.

21218718 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.

21218718 is a wasteful number, since it uses less digits than its factorization.

21218718 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3536458.

The product of its digits is 1792, while the sum is 30.

The square root of 21218718 is about 4606.3779697285. The cubic root of 21218718 is about 276.8469311177.

The spelling of 21218718 in words is "twenty-one million, two hundred eighteen thousand, seven hundred eighteen".