9990872821 has 4 divisors (see below), whose sum is σ = 9994397292. Its totient is φ = 9987348352.

The previous prime is 9990872819. The next prime is 9990872831. The reversal of 9990872821 is 1282780999.

9990872821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4152384721 + 5838488100 = 64439^2 + 76410^2 .

It is a cyclic number.

It is not a de Polignac number, because 9990872821 - 2¹ = 9990872819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9990872831) 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 in 3 ways as a sum of consecutive naturals, for example, 1757980 + ... + 1763653.

It is an arithmetic number, because the mean of its divisors is an integer number (2498599323).

Almost surely, 2^9990872821 is an apocalyptic number.

It is an amenable number.

9990872821 is a deficient number, since it is larger than the sum of its proper divisors (3524471).

9990872821 is a wasteful number, since it uses less digits than its factorization.

9990872821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3524470.

The product of its (nonzero) digits is 1306368, while the sum is 55.

The square root of 9990872821 is about 99954.3536870706. The cubic root of 9990872821 is about 2153.7790268109.

The spelling of 9990872821 in words is "nine billion, nine hundred ninety million, eight hundred seventy-two thousand, eight hundred twenty-one".