218490640 has 80 divisors (see below), whose sum is σ = 538559280. Its totient is φ = 82288640.

The previous prime is 218490617. The next prime is 218490653. The reversal of 218490640 is 46094812.

It can be written as a sum of positive squares in 8 ways, for example, as 26501904 + 191988736 = 5148^2 + 13856^2 .

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 218490596 and 218490605.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 93972 + ... + 96268.

It is an arithmetic number, because the mean of its divisors is an integer number (6731991).

Almost surely, 2^218490640 is an apocalyptic number.

218490640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 218490640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (269279640).

218490640 is an abundant number, since it is smaller than the sum of its proper divisors (320068640).

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

218490640 is a wasteful number, since it uses less digits than its factorization.

218490640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2380 (or 2374 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 218490640 is about 14781.4288889809. The cubic root of 218490640 is about 602.2973406315.

The spelling of 218490640 in words is "two hundred eighteen million, four hundred ninety thousand, six hundred forty".