641221218 has 64 divisors (see below), whose sum is σ = 1560643200. Its totient is φ = 193538880.

The previous prime is 641221199. The next prime is 641221219. The reversal of 641221218 is 812122146.

641221218 is a `hidden beast` number, since 641 + 2 + 2 + 1 + 2 + 18 = 666.

It is a super-2 number, since 2×641221218² = 822329300826807048, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 641221191 and 641221200.

It is not an unprimeable number, because it can be changed into a prime (641221219) 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 31 ways as a sum of consecutive naturals, for example, 157780 + ... + 161792.

It is an arithmetic number, because the mean of its divisors is an integer number (24385050).

Almost surely, 2^641221218 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 641221218, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (780321600).

641221218 is an abundant number, since it is smaller than the sum of its proper divisors (919421982).

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

641221218 is a wasteful number, since it uses less digits than its factorization.

641221218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4304 (or 4298 counting only the distinct ones).

The product of its digits is 1536, while the sum is 27.

The square root of 641221218 is about 25322.3462183108. The cubic root of 641221218 is about 862.3216599134.

The spelling of 641221218 in words is "six hundred forty-one million, two hundred twenty-one thousand, two hundred eighteen".