1216811916 has 96 divisors (see below), whose sum is σ = 3236889600. Its totient is φ = 395176320.

The previous prime is 1216811887. The next prime is 1216811917. The reversal of 1216811916 is 6191186121.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (1216811917) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 681561 + ... + 683343.

It is an arithmetic number, because the mean of its divisors is an integer number (33717600).

Almost surely, 2^1216811916 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1216811916, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1618444800).

1216811916 is an abundant number, since it is smaller than the sum of its proper divisors (2020077684).

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

1216811916 is a wasteful number, since it uses less digits than its factorization.

1216811916 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1956 (or 1948 counting only the distinct ones).

The product of its digits is 5184, while the sum is 36.

The square root of 1216811916 is about 34882.8312497710. The cubic root of 1216811916 is about 1067.5981634341.

The spelling of 1216811916 in words is "one billion, two hundred sixteen million, eight hundred eleven thousand, nine hundred sixteen".