9871971810021 has 24 divisors (see below), whose sum is σ = 14530398344280. Its totient is φ = 6456322768896.

The previous prime is 9871971810017. The next prime is 9871971810101. The reversal of 9871971810021 is 1200181791789.

It can be written as a sum of positive squares in 4 ways, for example, as 7767586387521 + 2104385422500 = 2787039^2 + 1450650^2 .

It is not a de Polignac number, because 9871971810021 - 2² = 9871971810017 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 9871971810021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9871971810721) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2482185 + ... + 5089713.

It is an arithmetic number, because the mean of its divisors is an integer number (605433264345).

Almost surely, 2^{9871971810021} is an apocalyptic number.

It is an amenable number.

9871971810021 is a deficient number, since it is larger than the sum of its proper divisors (4658426534259).

9871971810021 is a wasteful number, since it uses less digits than its factorization.

9871971810021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2615525 (or 2615522 counting only the distinct ones).

The product of its (nonzero) digits is 508032, while the sum is 54.

The spelling of 9871971810021 in words is "nine trillion, eight hundred seventy-one billion, nine hundred seventy-one million, eight hundred ten thousand, twenty-one".