8121865644 has 144 divisors (see below), whose sum is σ = 21893639040. Its totient is φ = 2536285440.

The previous prime is 8121865627. The next prime is 8121865673. The reversal of 8121865644 is 4465681218.

It is a happy number.

8121865644 is a `hidden beast` number, since 8 + 1 + 2 + 1 + 86 + 564 + 4 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 8121865644.

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 153242722 + ... + 153242774.

It is an arithmetic number, because the mean of its divisors is an integer number (152039160).

Almost surely, 2^8121865644 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 8121865644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (10946819520).

8121865644 is an abundant number, since it is smaller than the sum of its proper divisors (13771773396).

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

8121865644 is a wasteful number, since it uses less digits than its factorization.

8121865644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245 (or 146 counting only the distinct ones).

The product of its digits is 368640, while the sum is 45.

The square root of 8121865644 is about 90121.3939306311. The cubic root of 8121865644 is about 2010.1043355657.

The spelling of 8121865644 in words is "eight billion, one hundred twenty-one million, eight hundred sixty-five thousand, six hundred forty-four".