21385218 has 16 divisors (see below), whose sum is σ = 45286560. Its totient is φ = 6709056.

The previous prime is 21385211. The next prime is 21385237. The reversal of 21385218 is 81258312.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21385211) 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, 104728 + ... + 104931.

It is an arithmetic number, because the mean of its divisors is an integer number (2830410).

Almost surely, 2^21385218 is an apocalyptic number.

21385218 is an abundant number, since it is smaller than the sum of its proper divisors (23901342).

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

21385218 is a wasteful number, since it uses less digits than its factorization.

21385218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 209681.

The product of its digits is 3840, while the sum is 30.

The square root of 21385218 is about 4624.4154225156. The cubic root of 21385218 is about 277.5691703229.

The spelling of 21385218 in words is "twenty-one million, three hundred eighty-five thousand, two hundred eighteen".