2165959944561 has 64 divisors (see below), whose sum is σ = 3586987212800. Its totient is φ = 1134505958400.

The previous prime is 2165959944553. The next prime is 2165959944581. The reversal of 2165959944561 is 1654499595612.

It is not a de Polignac number, because 2165959944561 - 2³ = 2165959944553 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 2165959944492 and 2165959944501.

It is not an unprimeable number, because it can be changed into a prime (2165959944581) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 78665445 + ... + 78692973.

It is an arithmetic number, because the mean of its divisors is an integer number (56046675200).

Almost surely, 2^{2165959944561} is an apocalyptic number.

2165959944561 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

2165959944561 is a deficient number, since it is larger than the sum of its proper divisors (1421027268239).

2165959944561 is a wasteful number, since it uses less digits than its factorization.

2165959944561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33950.

The product of its digits is 104976000, while the sum is 66.

The spelling of 2165959944561 in words is "two trillion, one hundred sixty-five billion, nine hundred fifty-nine million, nine hundred forty-four thousand, five hundred sixty-one".