2161947816 has 72 divisors (see below), whose sum is σ = 6811249770. Its totient is φ = 617698368.

The previous prime is 2161947811. The next prime is 2161947841. The reversal of 2161947816 is 6187491612.

2161947816 is a `hidden beast` number, since 2 + 161 + 9 + 478 + 16 = 666.

It can be written as a sum of positive squares in only one way, i.e., 2115080100 + 46867716 = 45990^2 + 6846^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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

It is not an unprimeable number, because it can be changed into a prime (2161947811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 302871 + ... + 309926.

Almost surely, 2^2161947816 is an apocalyptic number.

It is an amenable number.

2161947816 is an abundant number, since it is smaller than the sum of its proper divisors (4649301954).

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

2161947816 is a wasteful number, since it uses less digits than its factorization.

2161947816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 612823 (or 612809 counting only the distinct ones).

The product of its digits is 145152, while the sum is 45.

The square root of 2161947816 is about 46496.7505961438. The cubic root of 2161947816 is about 1293.0492567587.

The spelling of 2161947816 in words is "two billion, one hundred sixty-one million, nine hundred forty-seven thousand, eight hundred sixteen".