661641564664 has 32 divisors (see below), whose sum is σ = 1250069721120. Its totient is φ = 328291326976.

The previous prime is 661641564631. The next prime is 661641564707. The reversal of 661641564664 is 466465146166.

It is a happy number.

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, 3077712 + ... + 3285664.

It is an arithmetic number, because the mean of its divisors is an integer number (39064678785).

Almost surely, 2^661641564664 is an apocalyptic number.

It is an amenable number.

661641564664 is a deficient number, since it is larger than the sum of its proper divisors (588428156456).

661641564664 is a wasteful number, since it uses less digits than its factorization.

661641564664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210999 (or 210995 counting only the distinct ones).

The product of its digits is 14929920, while the sum is 55.

The spelling of 661641564664 in words is "six hundred sixty-one billion, six hundred forty-one million, five hundred sixty-four thousand, six hundred sixty-four".