216821808 has 120 divisors (see below), whose sum is σ = 734336928. Its totient is φ = 58300416.

The previous prime is 216821807. The next prime is 216821809. The reversal of 216821808 is 808128612.

It is an interprime number because it is at equal distance from previous prime (216821807) and next prime (216821809).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (216821807) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10810 + ... + 23462.

Almost surely, 2^216821808 is an apocalyptic number.

216821808 is a gapful number since it is divisible by the number (28) 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 216821808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (367168464).

216821808 is an abundant number, since it is smaller than the sum of its proper divisors (517515120).

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

216821808 is a wasteful number, since it uses less digits than its factorization.

216821808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12691 (or 12682 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 36.

The square root of 216821808 is about 14724.8703899219. The cubic root of 216821808 is about 600.7599703354.

The spelling of 216821808 in words is "two hundred sixteen million, eight hundred twenty-one thousand, eight hundred eight".