218721864 has 64 divisors (see below), whose sum is σ = 597680640. Its totient is φ = 66401280.

The previous prime is 218721829. The next prime is 218721869. The reversal of 218721864 is 468127812.

It is a happy number.

It is a hoax number, since the sum of its digits (39) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (218721869) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4002 + ... + 21294.

It is an arithmetic number, because the mean of its divisors is an integer number (9338760).

Almost surely, 2^218721864 is an apocalyptic number.

218721864 is a gapful number since it is divisible by the number (24) 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 218721864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (298840320).

218721864 is an abundant number, since it is smaller than the sum of its proper divisors (378958776).

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

218721864 is a wasteful number, since it uses less digits than its factorization.

218721864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17350 (or 17346 counting only the distinct ones).

The product of its digits is 43008, while the sum is 39.

The square root of 218721864 is about 14789.2482567573. The cubic root of 218721864 is about 602.5097318837.

The spelling of 218721864 in words is "two hundred eighteen million, seven hundred twenty-one thousand, eight hundred sixty-four".