661555706065 has 8 divisors (see below), whose sum is σ = 796403164968. Its totient is φ = 527553686400.

The previous prime is 661555706059. The next prime is 661555706069. The reversal of 661555706065 is 560607555166.

661555706065 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 43250273089 + 618305432976 = 207967^2 + 786324^2 .

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

It is not a de Polignac number, because 661555706065 - 2¹⁵ = 661555673297 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661555706069) 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, 211358086 + ... + 211361215.

It is an arithmetic number, because the mean of its divisors is an integer number (99550395621).

Almost surely, 2^661555706065 is an apocalyptic number.

It is an amenable number.

661555706065 is a deficient number, since it is larger than the sum of its proper divisors (134847458903).

661555706065 is a wasteful number, since it uses less digits than its factorization.

661555706065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 422719619.

The product of its (nonzero) digits is 5670000, while the sum is 52.

The spelling of 661555706065 in words is "six hundred sixty-one billion, five hundred fifty-five million, seven hundred six thousand, sixty-five".