8531998721 has 2 divisors, whose sum is σ = 8531998722. Its totient is φ = 8531998720.

The previous prime is 8531998711. The next prime is 8531998729. The reversal of 8531998721 is 1278991358.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7449588721 + 1082410000 = 86311^2 + 32900^2 .

It is a cyclic number.

It is not a de Polignac number, because 8531998721 - 2²⁶ = 8464889857 is a prime.

It is not a weakly prime, because it can be changed into another prime (8531998729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4265999360 + 4265999361.

It is an arithmetic number, because the mean of its divisors is an integer number (4265999361).

Almost surely, 2^8531998721 is an apocalyptic number.

It is an amenable number.

8531998721 is a deficient number, since it is larger than the sum of its proper divisors (1).

8531998721 is an equidigital number, since it uses as much as digits as its factorization.

8531998721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1088640, while the sum is 53.

The square root of 8531998721 is about 92368.8189867122. The cubic root of 8531998721 is about 2043.3852802013.

The spelling of 8531998721 in words is "eight billion, five hundred thirty-one million, nine hundred ninety-eight thousand, seven hundred twenty-one".