261663555156 has 12 divisors (see below), whose sum is σ = 610548295392. Its totient is φ = 87221185048.

The previous prime is 261663555137. The next prime is 261663555157. The reversal of 261663555156 is 651555366162.

It is a tau number, because it is divible by the number of its divisors (12).

It is a Smith number, since the sum of its digits (51) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 261663555099 and 261663555108.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261663555157) 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 3 ways as a sum of consecutive naturals, for example, 10902648120 + ... + 10902648143.

It is an arithmetic number, because the mean of its divisors is an integer number (50879024616).

Almost surely, 2^261663555156 is an apocalyptic number.

It is an amenable number.

261663555156 is an abundant number, since it is smaller than the sum of its proper divisors (348884740236).

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

261663555156 is a wasteful number, since it uses less digits than its factorization.

261663555156 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21805296270 (or 21805296268 counting only the distinct ones).

The product of its digits is 4860000, while the sum is 51.

The spelling of 261663555156 in words is "two hundred sixty-one billion, six hundred sixty-three million, five hundred fifty-five thousand, one hundred fifty-six".