221218000 has 40 divisors (see below), whose sum is σ = 534909960. Its totient is φ = 88486400.

The previous prime is 221217989. The next prime is 221218027. The reversal of 221218000 is 812122.

It can be written as a sum of positive squares in 4 ways, for example, as 41616 + 221176384 = 204^2 + 14872^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 53305 + ... + 57304.

It is an arithmetic number, because the mean of its divisors is an integer number (13372749).

Almost surely, 2^221218000 is an apocalyptic number.

221218000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

221218000 is an abundant number, since it is smaller than the sum of its proper divisors (313691960).

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

221218000 is a wasteful number, since it uses less digits than its factorization.

221218000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110632 (or 110616 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 221218000 is about 14873.3990735138. The cubic root of 221218000 is about 604.7930900034.

The spelling of 221218000 in words is "two hundred twenty-one million, two hundred eighteen thousand".