661828808656 has 20 divisors (see below), whose sum is σ = 1293641048772. Its totient is φ = 327985957376.

The previous prime is 661828808633. The next prime is 661828808657. The reversal of 661828808656 is 656808828166.

It can be written as a sum of positive squares in 2 ways, for example, as 9908211600 + 651920597056 = 99540^2 + 807416^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661828808657) 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, 183026071 + ... + 183029686.

Almost surely, 2^661828808656 is an apocalyptic number.

It is an amenable number.

661828808656 is a deficient number, since it is larger than the sum of its proper divisors (631812240116).

661828808656 is a wasteful number, since it uses less digits than its factorization.

661828808656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 366055878 (or 366055872 counting only the distinct ones).

The product of its (nonzero) digits is 53084160, while the sum is 64.

The spelling of 661828808656 in words is "six hundred sixty-one billion, eight hundred twenty-eight million, eight hundred eight thousand, six hundred fifty-six".