9999171820 has 48 divisors (see below), whose sum is σ = 22922258688. Its totient is φ = 3633671360.

The previous prime is 9999171803. The next prime is 9999171827. The reversal of 9999171820 is 281719999.

9999171820 is a nontrivial binomial coefficient, being equal to C(141416, 2).

It is a super-2 number, since 2×9999171820² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (55).

It is not an unprimeable number, because it can be changed into a prime (9999171827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 339399 + ... + 367681.

It is an arithmetic number, because the mean of its divisors is an integer number (477547056).

Almost surely, 2^9999171820 is an apocalyptic number.

9999171820 is the 141415-th triangular number and also the 70708-th hexagonal number.

9999171820 is the 47139-th centered nonagonal number.

It is an amenable number.

9999171820 is an abundant number, since it is smaller than the sum of its proper divisors (12923086868).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

9999171820 is a wasteful number, since it uses less digits than its factorization.

9999171820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29910 (or 29908 counting only the distinct ones).

The product of its (nonzero) digits is 734832, while the sum is 55.

The square root of 9999171820 is about 99995.8590142612. The cubic root of 9999171820 is about 2154.3752130659.

The spelling of 9999171820 in words is "nine billion, nine hundred ninety-nine million, one hundred seventy-one thousand, eight hundred twenty".