661241280544 has 48 divisors (see below), whose sum is σ = 1402081192512. Its totient is φ = 305161613568.

The previous prime is 661241280533. The next prime is 661241280571. The reversal of 661241280544 is 445082142166.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 661241280544.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5171367 + ... + 5297689.

It is an arithmetic number, because the mean of its divisors is an integer number (29210024844).

Almost surely, 2^661241280544 is an apocalyptic number.

It is an amenable number.

661241280544 is an abundant number, since it is smaller than the sum of its proper divisors (740839911968).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661241280544 is a wasteful number, since it uses less digits than its factorization.

661241280544 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138929 (or 138921 counting only the distinct ones).

The product of its (nonzero) digits is 368640, while the sum is 43.

The spelling of 661241280544 in words is "six hundred sixty-one billion, two hundred forty-one million, two hundred eighty thousand, five hundred forty-four".