216781764 has 12 divisors (see below), whose sum is σ = 505824144. Its totient is φ = 72260584.

The previous prime is 216781751. The next prime is 216781771. The reversal of 216781764 is 467187612.

It is a tau number, because it is divible by the number of its divisors (12).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9032562 + ... + 9032585.

It is an arithmetic number, because the mean of its divisors is an integer number (42152012).

Almost surely, 2^216781764 is an apocalyptic number.

It is an amenable number.

216781764 is an abundant number, since it is smaller than the sum of its proper divisors (289042380).

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

216781764 is a wasteful number, since it uses less digits than its factorization.

216781764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18065154 (or 18065152 counting only the distinct ones).

The product of its digits is 112896, while the sum is 42.

The square root of 216781764 is about 14723.5105868132. The cubic root of 216781764 is about 600.7229840291.

The spelling of 216781764 in words is "two hundred sixteen million, seven hundred eighty-one thousand, seven hundred sixty-four".