661569280720 has 20 divisors (see below), whose sum is σ = 1538148577860. Its totient is φ = 264627712256.

The previous prime is 661569280667. The next prime is 661569280739. The reversal of 661569280720 is 27082965166.

It can be written as a sum of positive squares in 2 ways, for example, as 146171640976 + 515397639744 = 382324^2 + 717912^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4134807925 + ... + 4134808084.

It is an arithmetic number, because the mean of its divisors is an integer number (76907428893).

Almost surely, 2^661569280720 is an apocalyptic number.

It is an amenable number.

661569280720 is an abundant number, since it is smaller than the sum of its proper divisors (876579297140).

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

661569280720 is a wasteful number, since it uses less digits than its factorization.

661569280720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8269616022 (or 8269616016 counting only the distinct ones).

The product of its (nonzero) digits is 2177280, while the sum is 52.

The spelling of 661569280720 in words is "six hundred sixty-one billion, five hundred sixty-nine million, two hundred eighty thousand, seven hundred twenty".