998309981 has 2 divisors, whose sum is σ = 998309982. Its totient is φ = 998309980.

The previous prime is 998309971. The next prime is 998309993. The reversal of 998309981 is 189903899.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 552720100 + 445589881 = 23510^2 + 21109^2 .

It is an emirp because it is prime and its reverse (189903899) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 998309981 - 2¹⁰ = 998308957 is a prime.

It is a super-2 number, since 2×998309981² = 1993245636328440722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (998309971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499154990 + 499154991.

It is an arithmetic number, because the mean of its divisors is an integer number (499154991).

Almost surely, 2^998309981 is an apocalyptic number.

It is an amenable number.

998309981 is a deficient number, since it is larger than the sum of its proper divisors (1).

998309981 is an equidigital number, since it uses as much as digits as its factorization.

998309981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1259712, while the sum is 56.

The square root of 998309981 is about 31596.0437555084. The cubic root of 998309981 is about 999.4363426835.

The spelling of 998309981 in words is "nine hundred ninety-eight million, three hundred nine thousand, nine hundred eighty-one".