218421840 has 320 divisors, whose sum is σ = 850945536. Its totient is φ = 45121536.

The previous prime is 218421751. The next prime is 218421871. The reversal of 218421840 is 48124812.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 218421798 and 218421807.

It is a congruent number.

It is an unprimeable number.

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 63 ways as a sum of consecutive naturals, for example, 1594252 + ... + 1594388.

Almost surely, 2^218421840 is an apocalyptic number.

218421840 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 218421840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (425472768).

218421840 is an abundant number, since it is smaller than the sum of its proper divisors (632523696).

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

218421840 is a wasteful number, since it uses less digits than its factorization.

218421840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 246 (or 240 counting only the distinct ones).

The product of its (nonzero) digits is 4096, while the sum is 30.

The square root of 218421840 is about 14779.1014611850. The cubic root of 218421840 is about 602.2341153338.

The spelling of 218421840 in words is "two hundred eighteen million, four hundred twenty-one thousand, eight hundred forty".