216561617 has 8 divisors (see below), whose sum is σ = 218190024. Its totient is φ = 214939648.

The previous prime is 216561607. The next prime is 216561619. The reversal of 216561617 is 716165612.

It can be written as a sum of positive squares in 4 ways, for example, as 961 + 216560656 = 31^2 + 14716^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 216561617 - 2¹² = 216557521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216561619) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 80933 + ... + 83565.

It is an arithmetic number, because the mean of its divisors is an integer number (27273753).

Almost surely, 2^216561617 is an apocalyptic number.

It is an amenable number.

216561617 is a deficient number, since it is larger than the sum of its proper divisors (1628407).

216561617 is a wasteful number, since it uses less digits than its factorization.

216561617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3219.

The product of its digits is 15120, while the sum is 35.

The square root of 216561617 is about 14716.0326514995. The cubic root of 216561617 is about 600.5195656967.

The spelling of 216561617 in words is "two hundred sixteen million, five hundred sixty-one thousand, six hundred seventeen".