1216861128 has 96 divisors (see below), whose sum is σ = 3854136000. Its totient is φ = 339583104.

The previous prime is 1216861111. The next prime is 1216861147. The reversal of 1216861128 is 8211686121.

1216861128 is a `hidden beast` number, since 1 + 2 + 16 + 8 + 611 + 28 = 666.

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

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 1216861092 and 1216861101.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6403 + ... + 49746.

It is an arithmetic number, because the mean of its divisors is an integer number (40147250).

Almost surely, 2^1216861128 is an apocalyptic number.

1216861128 is a gapful number since it is divisible by the number (18) 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 1216861128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1927068000).

1216861128 is an abundant number, since it is smaller than the sum of its proper divisors (2637274872).

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

1216861128 is a wasteful number, since it uses less digits than its factorization.

1216861128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56211 (or 56204 counting only the distinct ones).

The product of its digits is 9216, while the sum is 36.

The square root of 1216861128 is about 34883.5366326294. The cubic root of 1216861128 is about 1067.6125556700.

The spelling of 1216861128 in words is "one billion, two hundred sixteen million, eight hundred sixty-one thousand, one hundred twenty-eight".