661637532566 has 48 divisors (see below), whose sum is σ = 1061538670080. Its totient is φ = 308700952560.

The previous prime is 661637532473. The next prime is 661637532583. The reversal of 661637532566 is 665235736166.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 77479925 + ... + 77488463.

It is an arithmetic number, because the mean of its divisors is an integer number (22115388960).

Almost surely, 2^661637532566 is an apocalyptic number.

661637532566 is a deficient number, since it is larger than the sum of its proper divisors (399901137514).

661637532566 is a wasteful number, since it uses less digits than its factorization.

661637532566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9561 (or 9518 counting only the distinct ones).

The product of its digits is 24494400, while the sum is 56.

The spelling of 661637532566 in words is "six hundred sixty-one billion, six hundred thirty-seven million, five hundred thirty-two thousand, five hundred sixty-six".