661720666616 has 32 divisors (see below), whose sum is σ = 1284876552960. Its totient is φ = 319272328032.

The previous prime is 661720666603. The next prime is 661720666637. The reversal of 661720666616 is 616666027166.

It is a congruent number.

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, 11559440 + ... + 11616543.

It is an arithmetic number, because the mean of its divisors is an integer number (40152392280).

Almost surely, 2^661720666616 is an apocalyptic number.

It is an amenable number.

661720666616 is a deficient number, since it is larger than the sum of its proper divisors (623155886344).

661720666616 is a wasteful number, since it uses less digits than its factorization.

661720666616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23176115 (or 23176111 counting only the distinct ones).

The product of its (nonzero) digits is 3919104, while the sum is 53.

The spelling of 661720666616 in words is "six hundred sixty-one billion, seven hundred twenty million, six hundred sixty-six thousand, six hundred sixteen".