661666786559 has 8 divisors (see below), whose sum is σ = 692367192192. Its totient is φ = 631551150720.

The previous prime is 661666786553. The next prime is 661666786579. The reversal of 661666786559 is 955687666166.

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

It is a cyclic number.

It is not a de Polignac number, because 661666786559 - 2⁸ = 661666786303 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 661666786492 and 661666786501.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661666786553) 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, 146190134 + ... + 146194659.

It is an arithmetic number, because the mean of its divisors is an integer number (86545899024).

Almost surely, 2^661666786559 is an apocalyptic number.

661666786559 is a deficient number, since it is larger than the sum of its proper divisors (30700405633).

661666786559 is a wasteful number, since it uses less digits than its factorization.

661666786559 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 292384897.

The product of its digits is 587865600, while the sum is 71.

The spelling of 661666786559 in words is "six hundred sixty-one billion, six hundred sixty-six million, seven hundred eighty-six thousand, five hundred fifty-nine".