9987839821 has 2 divisors, whose sum is σ = 9987839822. Its totient is φ = 9987839820.

The previous prime is 9987839783. The next prime is 9987839867. The reversal of 9987839821 is 1289387899.

9987839821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9987803721 + 36100 = 99939^2 + 190^2 .

It is a cyclic number.

It is not a de Polignac number, because 9987839821 - 2¹³ = 9987831629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9987834821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4993919910 + 4993919911.

It is an arithmetic number, because the mean of its divisors is an integer number (4993919911).

Almost surely, 2^9987839821 is an apocalyptic number.

It is an amenable number.

9987839821 is a deficient number, since it is larger than the sum of its proper divisors (1).

9987839821 is an equidigital number, since it uses as much as digits as its factorization.

9987839821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15676416, while the sum is 64.

The square root of 9987839821 is about 99939.1806100090. The cubic root of 9987839821 is about 2153.5610587699.

The spelling of 9987839821 in words is "nine billion, nine hundred eighty-seven million, eight hundred thirty-nine thousand, eight hundred twenty-one".