1216606665 has 8 divisors (see below), whose sum is σ = 1946570688. Its totient is φ = 648856880.

The previous prime is 1216606639. The next prime is 1216606673. The reversal of 1216606665 is 5666066121.

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

It is not a de Polignac number, because 1216606665 - 2¹⁷ = 1216475593 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40553541 + ... + 40553570.

It is an arithmetic number, because the mean of its divisors is an integer number (243321336).

Almost surely, 2^1216606665 is an apocalyptic number.

1216606665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1216606665 is a deficient number, since it is larger than the sum of its proper divisors (729964023).

1216606665 is an equidigital number, since it uses as much as digits as its factorization.

1216606665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81107119.

The product of its (nonzero) digits is 77760, while the sum is 39.

The square root of 1216606665 is about 34879.8891196632. The cubic root of 1216606665 is about 1067.5381328165.

The spelling of 1216606665 in words is "one billion, two hundred sixteen million, six hundred six thousand, six hundred sixty-five".