661565566 has 8 divisors (see below), whose sum is σ = 1005942384. Its totient is φ = 326251440.

The previous prime is 661565551. The next prime is 661565573. The reversal of 661565566 is 665565166.

It is a sphenic number, since it is the product of 3 distinct primes.

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, 2265490 + ... + 2265781.

It is an arithmetic number, because the mean of its divisors is an integer number (125742798).

Almost surely, 2^661565566 is an apocalyptic number.

661565566 is a deficient number, since it is larger than the sum of its proper divisors (344376818).

661565566 is a wasteful number, since it uses less digits than its factorization.

661565566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4531346.

The product of its digits is 972000, while the sum is 46.

The square root of 661565566 is about 25720.9168965649. The cubic root of 661565566 is about 871.3466466002.

The spelling of 661565566 in words is "six hundred sixty-one million, five hundred sixty-five thousand, five hundred sixty-six".