9721865559021 has 64 divisors (see below), whose sum is σ = 16287119456256. Its totient is φ = 5010927667200.

The previous prime is 9721865559017. The next prime is 9721865559041. The reversal of 9721865559021 is 1209555681279.

It is not a de Polignac number, because 9721865559021 - 2² = 9721865559017 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9721865559041) 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, 206749905 + ... + 206796921.

It is an arithmetic number, because the mean of its divisors is an integer number (254486241504).

Almost surely, 2^{9721865559021} is an apocalyptic number.

It is an amenable number.

9721865559021 is a deficient number, since it is larger than the sum of its proper divisors (6565253897235).

9721865559021 is a wasteful number, since it uses less digits than its factorization.

9721865559021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54002.

The product of its (nonzero) digits is 13608000, while the sum is 60.

The spelling of 9721865559021 in words is "nine trillion, seven hundred twenty-one billion, eight hundred sixty-five million, five hundred fifty-nine thousand, twenty-one".