8491973621 has 2 divisors, whose sum is σ = 8491973622. Its totient is φ = 8491973620.

The previous prime is 8491973593. The next prime is 8491973627. The reversal of 8491973621 is 1263791948.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7092166225 + 1399807396 = 84215^2 + 37414^2 .

It is a cyclic number.

It is not a de Polignac number, because 8491973621 - 2⁶ = 8491973557 is a prime.

It is a super-2 number, since 2×8491973621² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 8491973621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8491973627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4245986810 + 4245986811.

It is an arithmetic number, because the mean of its divisors is an integer number (4245986811).

Almost surely, 2^8491973621 is an apocalyptic number.

It is an amenable number.

8491973621 is a deficient number, since it is larger than the sum of its proper divisors (1).

8491973621 is an equidigital number, since it uses as much as digits as its factorization.

8491973621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 653184, while the sum is 50.

The square root of 8491973621 is about 92151.9051403714. The cubic root of 8491973621 is about 2040.1849778600.

The spelling of 8491973621 in words is "eight billion, four hundred ninety-one million, nine hundred seventy-three thousand, six hundred twenty-one".