218211840 has 640 divisors, whose sum is σ = 989936640. Its totient is φ = 44236800.

The previous prime is 218211839. The next prime is 218211853. The reversal of 218211840 is 48112812.

It is a tau number, because it is divible by the number of its divisors (640).

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 5322220 + ... + 5322260.

It is an arithmetic number, because the mean of its divisors is an integer number (1546776).

Almost surely, 2^218211840 is an apocalyptic number.

218211840 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 218211840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (494968320).

218211840 is an abundant number, since it is smaller than the sum of its proper divisors (771724800).

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

218211840 is a wasteful number, since it uses less digits than its factorization.

218211840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91 (or 69 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 27.

The square root of 218211840 is about 14771.9951259131. The cubic root of 218211840 is about 602.0410489921.

The spelling of 218211840 in words is "two hundred eighteen million, two hundred eleven thousand, eight hundred forty".