661009680740 has 24 divisors (see below), whose sum is σ = 1388291684472. Its totient is φ = 264371233280.

The previous prime is 661009680739. The next prime is 661009680787. The reversal of 661009680740 is 47086900166.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 111904968484 + 549104712256 = 334522^2 + 741016^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1873541 + ... + 2198220.

It is an arithmetic number, because the mean of its divisors is an integer number (57845486853).

Almost surely, 2^661009680740 is an apocalyptic number.

It is an amenable number.

661009680740 is an abundant number, since it is smaller than the sum of its proper divisors (727282003732).

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

661009680740 is a wasteful number, since it uses less digits than its factorization.

661009680740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4079887 (or 4079885 counting only the distinct ones).

The product of its (nonzero) digits is 435456, while the sum is 47.

The spelling of 661009680740 in words is "six hundred sixty-one billion, nine million, six hundred eighty thousand, seven hundred forty".