9999921939021 has 64 divisors (see below), whose sum is σ = 17516509286400. Its totient is φ = 5516696203200.

The previous prime is 9999921939017. The next prime is 9999921939037. The reversal of 9999921939021 is 1209391299999.

9999921939021 is a nontrivial binomial coefficient, being equal to C(4472119, 2).

It is not a de Polignac number, because 9999921939021 - 2² = 9999921939017 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9999921939071) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 64768606 + ... + 64922816.

It is an arithmetic number, because the mean of its divisors is an integer number (273695457600).

Almost surely, 2^{9999921939021} is an apocalyptic number.

9999921939021 is the 4472118-th triangular number.

It is an amenable number.

9999921939021 is a deficient number, since it is larger than the sum of its proper divisors (7516587347379).

9999921939021 is a wasteful number, since it uses less digits than its factorization.

9999921939021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166087 (or 166081 counting only the distinct ones).

The product of its (nonzero) digits is 57395628, while the sum is 72.

The spelling of 9999921939021 in words is "nine trillion, nine hundred ninety-nine billion, nine hundred twenty-one million, nine hundred thirty-nine thousand, twenty-one".