123661556543 has 16 divisors (see below), whose sum is σ = 142459699200. Its totient is φ = 105149632896.

The previous prime is 123661556531. The next prime is 123661556581. The reversal of 123661556543 is 345655166321.

It is a de Polignac number, because none of the positive numbers 2^k-123661556543 is a prime.

It is a super-2 number, since 2×123661556543² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (123661558543) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 337730 + ... + 601152.

It is an arithmetic number, because the mean of its divisors is an integer number (8903731200).

Almost surely, 2^123661556543 is an apocalyptic number.

123661556543 is a deficient number, since it is larger than the sum of its proper divisors (18798142657).

123661556543 is a wasteful number, since it uses less digits than its factorization.

123661556543 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 263966.

The product of its digits is 1944000, while the sum is 47.

The spelling of 123661556543 in words is "one hundred twenty-three billion, six hundred sixty-one million, five hundred fifty-six thousand, five hundred forty-three".