216617661 has 12 divisors (see below), whose sum is σ = 336960988. Its totient is φ = 133303104.

The previous prime is 216617641. The next prime is 216617693. The reversal of 216617661 is 166716612.

It can be written as a sum of positive squares in 2 ways, for example, as 35176761 + 181440900 = 5931^2 + 13470^2 .

It is not a de Polignac number, because 216617661 - 2¹¹ = 216615613 is a prime.

It is a super-2 number, since 2×216617661² = 93846422114221842, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216617641) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 925600 + ... + 925833.

Almost surely, 2^216617661 is an apocalyptic number.

It is an amenable number.

216617661 is a deficient number, since it is larger than the sum of its proper divisors (120343327).

216617661 is a wasteful number, since it uses less digits than its factorization.

216617661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1851452 (or 1851449 counting only the distinct ones).

The product of its digits is 18144, while the sum is 36.

The square root of 216617661 is about 14717.9367100148. The cubic root of 216617661 is about 600.5713640658.

The spelling of 216617661 in words is "two hundred sixteen million, six hundred seventeen thousand, six hundred sixty-one".