218211220 has 12 divisors (see below), whose sum is σ = 458243604. Its totient is φ = 87284480.

The previous prime is 218211211. The next prime is 218211221. The reversal of 218211220 is 22112812.

It can be written as a sum of positive squares in 2 ways, for example, as 94245264 + 123965956 = 9708^2 + 11134^2 .

It is a super-2 number, since 2×218211220² = 95232273067776800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (218211221) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 5455261 + ... + 5455300.

It is an arithmetic number, because the mean of its divisors is an integer number (38186967).

Almost surely, 2^218211220 is an apocalyptic number.

218211220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

218211220 is an abundant number, since it is smaller than the sum of its proper divisors (240032384).

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

218211220 is a wasteful number, since it uses less digits than its factorization.

218211220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10910570 (or 10910568 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 19.

The square root of 218211220 is about 14771.9741402427. The cubic root of 218211220 is about 602.0404788033.

The spelling of 218211220 in words is "two hundred eighteen million, two hundred eleven thousand, two hundred twenty".