9993815981 has 2 divisors, whose sum is σ = 9993815982. Its totient is φ = 9993815980.

The previous prime is 9993815971. The next prime is 9993815987. The reversal of 9993815981 is 1895183999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9971819881 + 21996100 = 99859^2 + 4690^2 .

It is a cyclic number.

It is not a de Polignac number, because 9993815981 - 2³⁰ = 8920074157 is a prime.

It is a super-2 number, since 2×9993815981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9993815987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4996907990 + 4996907991.

It is an arithmetic number, because the mean of its divisors is an integer number (4996907991).

Almost surely, 2^9993815981 is an apocalyptic number.

It is an amenable number.

9993815981 is a deficient number, since it is larger than the sum of its proper divisors (1).

9993815981 is an equidigital number, since it uses as much as digits as its factorization.

9993815981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6298560, while the sum is 62.

The square root of 9993815981 is about 99969.0751232600. The cubic root of 9993815981 is about 2153.9904962873.

The spelling of 9993815981 in words is "nine billion, nine hundred ninety-three million, eight hundred fifteen thousand, nine hundred eighty-one".