2165261343561 has 48 divisors (see below), whose sum is σ = 3281215863744. Its totient is φ = 1374602389632.

The previous prime is 2165261343551. The next prime is 2165261343571. The reversal of 2165261343561 is 1653431625612.

It is a happy number.

2165261343561 is a `hidden beast` number, since 2 + 1 + 6 + 5 + 261 + 34 + 356 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (2165261343551) and next prime (2165261343571).

It is not a de Polignac number, because 2165261343561 - 2³¹ = 2163113859913 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2165261343541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2591295 + ... + 3323451.

It is an arithmetic number, because the mean of its divisors is an integer number (68358663828).

Almost surely, 2^{2165261343561} is an apocalyptic number.

It is an amenable number.

2165261343561 is a deficient number, since it is larger than the sum of its proper divisors (1115954520183).

2165261343561 is a wasteful number, since it uses less digits than its factorization.

2165261343561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 732390 (or 732387 counting only the distinct ones).

The product of its digits is 777600, while the sum is 45.

The spelling of 2165261343561 in words is "two trillion, one hundred sixty-five billion, two hundred sixty-one million, three hundred forty-three thousand, five hundred sixty-one".