216721920 has 80 divisors (see below), whose sum is σ = 692857440. Its totient is φ = 57790464.

The previous prime is 216721907. The next prime is 216721943. The reversal of 216721920 is 29127612.

216721920 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

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

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

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6430 + ... + 21789.

It is an arithmetic number, because the mean of its divisors is an integer number (8660718).

Almost surely, 2^216721920 is an apocalyptic number.

216721920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

216721920 is an abundant number, since it is smaller than the sum of its proper divisors (476135520).

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

216721920 is an equidigital number, since it uses as much as digits as its factorization.

216721920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28245 (or 28229 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 30.

The square root of 216721920 is about 14721.4781866496. The cubic root of 216721920 is about 600.6677011275.

The spelling of 216721920 in words is "two hundred sixteen million, seven hundred twenty-one thousand, nine hundred twenty".