9991779841 has 2 divisors, whose sum is σ = 9991779842. Its totient is φ = 9991779840.

The previous prime is 9991779829. The next prime is 9991779871. The reversal of 9991779841 is 1489771999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 7906944241 + 2084835600 = 88921^2 + 45660^2 .

It is a cyclic number.

It is not a de Polignac number, because 9991779841 - 2¹⁹ = 9991255553 is a prime.

It is not a weakly prime, because it can be changed into another prime (9991779871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4995889920 + 4995889921.

It is an arithmetic number, because the mean of its divisors is an integer number (4995889921).

Almost surely, 2^9991779841 is an apocalyptic number.

It is an amenable number.

9991779841 is a deficient number, since it is larger than the sum of its proper divisors (1).

9991779841 is an equidigital number, since it uses as much as digits as its factorization.

9991779841 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10287648, while the sum is 64.

The square root of 9991779841 is about 99958.8907551499. The cubic root of 9991779841 is about 2153.8442016818.

The spelling of 9991779841 in words is "nine billion, nine hundred ninety-one million, seven hundred seventy-nine thousand, eight hundred forty-one".