2111561206521 has 12 divisors (see below), whose sum is σ = 3048644582928. Its totient is φ = 1299422280624.

The previous prime is 2111561206483. The next prime is 2111561206541. The reversal of 2111561206521 is 1256021651112.

It is a happy number.

It is not a de Polignac number, because 2111561206521 - 2¹⁸ = 2111560944377 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2111561206541) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2082406995 + ... + 2082408008.

It is an arithmetic number, because the mean of its divisors is an integer number (254053715244).

Almost surely, 2^{2111561206521} is an apocalyptic number.

It is an amenable number.

2111561206521 is a deficient number, since it is larger than the sum of its proper divisors (937083376407).

2111561206521 is a wasteful number, since it uses less digits than its factorization.

2111561206521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4164815032 (or 4164815019 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 33.

Adding to 2111561206521 its reverse (1256021651112), we get a palindrome (3367582857633).

The spelling of 2111561206521 in words is "two trillion, one hundred eleven billion, five hundred sixty-one million, two hundred six thousand, five hundred twenty-one".