11661561656565 has 16 divisors (see below), whose sum is σ = 18684815308800. Its totient is φ = 6210727330752.

The previous prime is 11661561656539. The next prime is 11661561656579. The reversal of 11661561656565 is 56565616516611.

It is a happy number.

It is not a de Polignac number, because 11661561656565 - 2¹⁵ = 11661561623797 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 11661561656499 and 11661561656508.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 548252725 + ... + 548273994.

It is an arithmetic number, because the mean of its divisors is an integer number (1167800956800).

Almost surely, 2^{11661561656565} is an apocalyptic number.

11661561656565 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

11661561656565 is a deficient number, since it is larger than the sum of its proper divisors (7023253652235).

11661561656565 is a wasteful number, since it uses less digits than its factorization.

11661561656565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1096527436.

The product of its digits is 29160000, while the sum is 60.

The spelling of 11661561656565 in words is "eleven trillion, six hundred sixty-one billion, five hundred sixty-one million, six hundred fifty-six thousand, five hundred sixty-five".