661643404394 has 16 divisors (see below), whose sum is σ = 1134270272256. Its totient is φ = 283555350000.

The previous prime is 661643404363. The next prime is 661643404417. The reversal of 661643404394 is 493404346166.

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, 197804 + ... + 1167224.

It is an arithmetic number, because the mean of its divisors is an integer number (70891892016).

Almost surely, 2^661643404394 is an apocalyptic number.

661643404394 is a deficient number, since it is larger than the sum of its proper divisors (472626867862).

661643404394 is a wasteful number, since it uses less digits than its factorization.

661643404394 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1018181.

The product of its (nonzero) digits is 4478976, while the sum is 50.

The spelling of 661643404394 in words is "six hundred sixty-one billion, six hundred forty-three million, four hundred four thousand, three hundred ninety-four".