216716681 has 4 divisors (see below), whose sum is σ = 224189700. Its totient is φ = 209243664.

The previous prime is 216716657. The next prime is 216716683. The reversal of 216716681 is 186617612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 107827456 + 108889225 = 10384^2 + 10435^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216716681 is a prime.

It is a super-2 number, since 2×216716681² = 93932239647311522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216716683) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3736466 + ... + 3736523.

It is an arithmetic number, because the mean of its divisors is an integer number (56047425).

Almost surely, 2^216716681 is an apocalyptic number.

It is an amenable number.

216716681 is a deficient number, since it is larger than the sum of its proper divisors (7473019).

216716681 is an equidigital number, since it uses as much as digits as its factorization.

216716681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7473018.

The product of its digits is 24192, while the sum is 38.

The square root of 216716681 is about 14721.3002482797. The cubic root of 216716681 is about 600.6628609411.

The spelling of 216716681 in words is "two hundred sixteen million, seven hundred sixteen thousand, six hundred eighty-one".