661558600061 has 4 divisors (see below), whose sum is σ = 674040837852. Its totient is φ = 649076362272.

The previous prime is 661558600057. The next prime is 661558600127. The reversal of 661558600061 is 160006855166.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 455901792025 + 205656808036 = 675205^2 + 453494^2 .

It is a cyclic number.

It is not a de Polignac number, because 661558600061 - 2² = 661558600057 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 661558599985 and 661558600021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661558600861) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6241118816 + ... + 6241118921.

It is an arithmetic number, because the mean of its divisors is an integer number (168510209463).

Almost surely, 2^661558600061 is an apocalyptic number.

It is an amenable number.

661558600061 is a deficient number, since it is larger than the sum of its proper divisors (12482237791).

661558600061 is a wasteful number, since it uses less digits than its factorization.

661558600061 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12482237790.

The product of its (nonzero) digits is 259200, while the sum is 44.

The spelling of 661558600061 in words is "six hundred sixty-one billion, five hundred fifty-eight million, six hundred thousand, sixty-one".