661555506698 has 4 divisors (see below), whose sum is σ = 992333260050. Its totient is φ = 330777753348.

The previous prime is 661555506643. The next prime is 661555506779. The reversal of 661555506698 is 896605555166.

661555506698 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 896605555166 = 2 ⋅448302777583.

It can be written as a sum of positive squares in only one way, i.e., 585994843009 + 75560663689 = 765503^2 + 274883^2 .

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 661555506698.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 165388876673 + ... + 165388876676.

Almost surely, 2^661555506698 is an apocalyptic number.

661555506698 is a deficient number, since it is larger than the sum of its proper divisors (330777753352).

661555506698 is a wasteful number, since it uses less digits than its factorization.

661555506698 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 330777753351.

The product of its (nonzero) digits is 58320000, while the sum is 62.

The spelling of 661555506698 in words is "six hundred sixty-one billion, five hundred fifty-five million, five hundred six thousand, six hundred ninety-eight".