11561561561 has 8 divisors (see below), whose sum is σ = 12618751104. Its totient is φ = 10505395120.

The previous prime is 11561561549. The next prime is 11561561581. The reversal of 11561561561 is 16516516511.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 11561561561 - 2¹⁰ = 11561560537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (11561561521) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 232046 + ... + 277431.

It is an arithmetic number, because the mean of its divisors is an integer number (1577343888).

Almost surely, 2^11561561561 is an apocalyptic number.

11561561561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

11561561561 is a deficient number, since it is larger than the sum of its proper divisors (1057189543).

11561561561 is a wasteful number, since it uses less digits than its factorization.

11561561561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 511551.

The product of its digits is 27000, while the sum is 38.

The spelling of 11561561561 in words is "eleven billion, five hundred sixty-one million, five hundred sixty-one thousand, five hundred sixty-one".