216501665 has 4 divisors (see below), whose sum is σ = 259802004. Its totient is φ = 173201328.

The previous prime is 216501643. The next prime is 216501679. The reversal of 216501665 is 566105612.

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 99840064 + 116661601 = 9992^2 + 10801^2 .

It is a cyclic number.

It is not a de Polignac number, because 216501665 - 2⁶ = 216501601 is a prime.

It is a Duffinian number.

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, 21650162 + ... + 21650171.

It is an arithmetic number, because the mean of its divisors is an integer number (64950501).

Almost surely, 2^216501665 is an apocalyptic number.

It is an amenable number.

216501665 is a deficient number, since it is larger than the sum of its proper divisors (43300339).

216501665 is an equidigital number, since it uses as much as digits as its factorization.

216501665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43300338.

The product of its (nonzero) digits is 10800, while the sum is 32.

The square root of 216501665 is about 14713.9955484566. The cubic root of 216501665 is about 600.4641454853.

The spelling of 216501665 in words is "two hundred sixteen million, five hundred one thousand, six hundred sixty-five".