9811998672921 has 27 divisors (see below), whose sum is σ = 14409880119453. Its totient is φ = 6433721601120.

The previous prime is 9811998672881. The next prime is 9811998672947. The reversal of 9811998672921 is 1292768991189.

The square root of 9811998672921 is 3132411.

It is a perfect power (a square), and thus also a powerful number.

9811998672921 is a `hidden beast` number, since 98 + 1 + 199 + 8 + 67 + 292 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 9370486265625 + 441512407296 = 3061125^2 + 664464^2 .

It is not a de Polignac number, because 9811998672921 - 2³⁷ = 9674559719449 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 9811998672921.

It is not an unprimeable number, because it can be changed into a prime (9811998674921) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 573222655 + ... + 573239771.

Almost surely, 2^{9811998672921} is an apocalyptic number.

9811998672921 is the 3132411-st square number.

9811998672921 is the 1566206-th centered octagonal number.

It is an amenable number.

9811998672921 is a deficient number, since it is larger than the sum of its proper divisors (4597881446532).

9811998672921 is an frugal number, since it uses more digits than its factorization.

9811998672921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34362 (or 17181 counting only the distinct ones).

The product of its digits is 70543872, while the sum is 72.

The spelling of 9811998672921 in words is "nine trillion, eight hundred eleven billion, nine hundred ninety-eight million, six hundred seventy-two thousand, nine hundred twenty-one".