216821680 has 80 divisors (see below), whose sum is σ = 516645504. Its totient is φ = 84602880.

The previous prime is 216821677. The next prime is 216821681. The reversal of 216821680 is 86128612.

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

It is not an unprimeable number, because it can be changed into a prime (216821681) 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, 799945 + ... + 800215.

Almost surely, 2^216821680 is an apocalyptic number.

216821680 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 216821680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (258322752).

216821680 is an abundant number, since it is smaller than the sum of its proper divisors (299823824).

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

216821680 is a wasteful number, since it uses less digits than its factorization.

216821680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 494 (or 488 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 34.

The square root of 216821680 is about 14724.8660435333. The cubic root of 216821680 is about 600.7598521165.

The spelling of 216821680 in words is "two hundred sixteen million, eight hundred twenty-one thousand, six hundred eighty".