1216111616 has 44 divisors (see below), whose sum is σ = 2471015580. Its totient is φ = 598056960.

The previous prime is 1216111613. The next prime is 1216111621. The reversal of 1216111616 is 6161116121.

It can be written as a sum of positive squares in 2 ways, for example, as 198246400 + 1017865216 = 14080^2 + 31904^2 .

It is not an unprimeable number, because it can be changed into a prime (1216111613) 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, 52730 + ... + 72198.

It is an arithmetic number, because the mean of its divisors is an integer number (56159445).

Almost surely, 2^1216111616 is an apocalyptic number.

1216111616 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1216111616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1235507790).

1216111616 is an abundant number, since it is smaller than the sum of its proper divisors (1254903964).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1216111616 is an equidigital number, since it uses as much as digits as its factorization.

1216111616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19550 (or 19532 counting only the distinct ones).

The product of its digits is 432, while the sum is 26.

The square root of 1216111616 is about 34872.7919157615. The cubic root of 1216111616 is about 1067.3933159807.

Adding to 1216111616 its reverse (6161116121), we get a palindrome (7377227737).

The spelling of 1216111616 in words is "one billion, two hundred sixteen million, one hundred eleven thousand, six hundred sixteen".