1216318861 has 4 divisors (see below), whose sum is σ = 1228361724. Its totient is φ = 1204276000.

The previous prime is 1216318853. The next prime is 1216318903. The reversal of 1216318861 is 1688136121.

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 966836836 + 249482025 = 31094^2 + 15795^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216318861 - 2³ = 1216318853 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1216318861.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216318811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6021280 + ... + 6021481.

It is an arithmetic number, because the mean of its divisors is an integer number (307090431).

Almost surely, 2^1216318861 is an apocalyptic number.

It is an amenable number.

1216318861 is a deficient number, since it is larger than the sum of its proper divisors (12042863).

1216318861 is a wasteful number, since it uses less digits than its factorization.

1216318861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12042862.

The product of its digits is 13824, while the sum is 37.

The square root of 1216318861 is about 34875.7632317918. The cubic root of 1216318861 is about 1067.4539462057.

The spelling of 1216318861 in words is "one billion, two hundred sixteen million, three hundred eighteen thousand, eight hundred sixty-one".