491217305661 has 20 divisors (see below), whose sum is σ = 733836444000. Its totient is φ = 327459151656.

The previous prime is 491217305639. The next prime is 491217305669. The reversal of 491217305661 is 166503712194.

491217305661 is a `hidden beast` number, since 4 + 9 + 12 + 1 + 73 + 0 + 566 + 1 = 666.

It is not a de Polignac number, because 491217305661 - 2¹⁸ = 491217043517 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (491217305669) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1300290 + ... + 1634988.

It is an arithmetic number, because the mean of its divisors is an integer number (36691822200).

Almost surely, 2^491217305661 is an apocalyptic number.

It is an amenable number.

491217305661 is a deficient number, since it is larger than the sum of its proper divisors (242619138339).

491217305661 is a wasteful number, since it uses less digits than its factorization.

491217305661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 352830 (or 352821 counting only the distinct ones).

The product of its (nonzero) digits is 272160, while the sum is 45.

The spelling of 491217305661 in words is "four hundred ninety-one billion, two hundred seventeen million, three hundred five thousand, six hundred sixty-one".