4991999981 has 2 divisors, whose sum is σ = 4991999982. Its totient is φ = 4991999980.

The previous prime is 4991999963. The next prime is 4991999993. The reversal of 4991999981 is 1899991994.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2638876900 + 2353123081 = 51370^2 + 48509^2 .

It is a cyclic number.

It is not a de Polignac number, because 4991999981 - 2⁶ = 4991999917 is a prime.

It is a super-2 number, since 2×4991999981² = 49840127620608000722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (4991999911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2495999990 + 2495999991.

It is an arithmetic number, because the mean of its divisors is an integer number (2495999991).

Almost surely, 2^4991999981 is an apocalyptic number.

It is an amenable number.

4991999981 is a deficient number, since it is larger than the sum of its proper divisors (1).

4991999981 is an equidigital number, since it uses as much as digits as its factorization.

4991999981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17006112, while the sum is 68.

The square root of 4991999981 is about 70654.0867961649. The cubic root of 4991999981 is about 1709.0634705109.

The spelling of 4991999981 in words is "four billion, nine hundred ninety-one million, nine hundred ninety-nine thousand, nine hundred eighty-one".