8491973661 has 10 divisors (see below), whose sum is σ = 12685541022. Its totient is φ = 5661315720.

The previous prime is 8491973653. The next prime is 8491973683. The reversal of 8491973661 is 1663791948.

8491973661 is a `hidden beast` number, since 8 + 491 + 97 + 3 + 6 + 61 = 666.

It can be written as a sum of positive squares in only one way, i.e., 8246456100 + 245517561 = 90810^2 + 15669^2 .

It is not a de Polignac number, because 8491973661 - 2³ = 8491973653 is a prime.

It is a super-2 number, since 2×8491973661² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 8491973598 and 8491973607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8491973621) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 52419510 + ... + 52419671.

Almost surely, 2^8491973661 is an apocalyptic number.

8491973661 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

8491973661 is a deficient number, since it is larger than the sum of its proper divisors (4193567361).

8491973661 is a wasteful number, since it uses less digits than its factorization.

8491973661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104839193 (or 104839184 counting only the distinct ones).

The product of its digits is 1959552, while the sum is 54.

The square root of 8491973661 is about 92151.9053574043. The cubic root of 8491973661 is about 2040.1849810633.

The spelling of 8491973661 in words is "eight billion, four hundred ninety-one million, nine hundred seventy-three thousand, six hundred sixty-one".