9999920021 has 16 divisors (see below), whose sum is σ = 12310066944. Its totient is φ = 7910434944.

The previous prime is 9999920011. The next prime is 9999920057. The reversal of 9999920021 is 1200299999.

It is a cyclic number.

It is not a de Polignac number, because 9999920021 - 2²⁶ = 9932811157 is a prime.

It is a Smith number, since the sum of its digits (50) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9999920011) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 682256 + ... + 696758.

It is an arithmetic number, because the mean of its divisors is an integer number (769379184).

Almost surely, 2^9999920021 is an apocalyptic number.

9999920021 is a gapful number since it is divisible by the number (91) formed by its first and last digit.

It is an amenable number.

9999920021 is a deficient number, since it is larger than the sum of its proper divisors (2310146923).

9999920021 is a wasteful number, since it uses less digits than its factorization.

9999920021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22100.

The product of its (nonzero) digits is 236196, while the sum is 50.

The square root of 9999920021 is about 99999.6001042004. The cubic root of 9999920021 is about 2154.4289463655.

The spelling of 9999920021 in words is "nine billion, nine hundred ninety-nine million, nine hundred twenty thousand, twenty-one".