661156651566 has 24 divisors (see below), whose sum is σ = 1439704609200. Its totient is φ = 219278084256.

The previous prime is 661156651543. The next prime is 661156651591. The reversal of 661156651566 is 665156651166.

661156651566 is a `hidden beast` number, since 6 + 6 + 1 + 1 + 5 + 66 + 515 + 66 = 666.

It is a congruent number.

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 11 ways as a sum of consecutive naturals, for example, 92285175 + ... + 92292338.

It is an arithmetic number, because the mean of its divisors is an integer number (59987692050).

Almost surely, 2^661156651566 is an apocalyptic number.

661156651566 is an abundant number, since it is smaller than the sum of its proper divisors (778547957634).

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

661156651566 is a wasteful number, since it uses less digits than its factorization.

661156651566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 184577720 (or 184577717 counting only the distinct ones).

The product of its digits is 5832000, while the sum is 54.

The spelling of 661156651566 in words is "six hundred sixty-one billion, one hundred fifty-six million, six hundred fifty-one thousand, five hundred sixty-six".