21457218 has 16 divisors (see below), whose sum is σ = 43041600. Its totient is φ = 7131216.

The previous prime is 21457207. The next prime is 21457253. The reversal of 21457218 is 81275412.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3030 + ... + 7217.

It is an arithmetic number, because the mean of its divisors is an integer number (2690100).

Almost surely, 2^21457218 is an apocalyptic number.

21457218 is an abundant number, since it is smaller than the sum of its proper divisors (21584382).

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

21457218 is a wasteful number, since it uses less digits than its factorization.

21457218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10601.

The product of its digits is 4480, while the sum is 30.

The square root of 21457218 is about 4632.1936488018. The cubic root of 21457218 is about 277.8803290802.

The spelling of 21457218 in words is "twenty-one million, four hundred fifty-seven thousand, two hundred eighteen".