216665945 has 4 divisors (see below), whose sum is σ = 259999140. Its totient is φ = 173332752.

The previous prime is 216665941. The next prime is 216665947. The reversal of 216665945 is 549566612.

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 87684496 + 128981449 = 9364^2 + 11357^2 .

It is a cyclic number.

It is not a de Polignac number, because 216665945 - 2² = 216665941 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 216665896 and 216665905.

It is not an unprimeable number, because it can be changed into a prime (216665941) 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, 21666590 + ... + 21666599.

It is an arithmetic number, because the mean of its divisors is an integer number (64999785).

Almost surely, 2^216665945 is an apocalyptic number.

It is an amenable number.

216665945 is a deficient number, since it is larger than the sum of its proper divisors (43333195).

216665945 is an equidigital number, since it uses as much as digits as its factorization.

216665945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43333194.

The product of its digits is 388800, while the sum is 44.

The square root of 216665945 is about 14719.5769300615. The cubic root of 216665945 is about 600.6159831323.

The spelling of 216665945 in words is "two hundred sixteen million, six hundred sixty-five thousand, nine hundred forty-five".