19644937572121 has 27 divisors (see below), whose sum is σ = 20741438726463. Its totient is φ = 18604858773600.

The previous prime is 19644937572089. The next prime is 19644937572133. The reversal of 19644937572121 is 12127573944691.

The square root of 19644937572121 is 4432261.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 2551012701721 + 17093924870400 = 1597189^2 + 4134480^2 .

It is not a de Polignac number, because 19644937572121 - 2⁵ = 19644937572089 is a prime.

It is a super-3 number, since 3×19644937572121³ (a number of 41 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 19644937572121.

It is not an unprimeable number, because it can be changed into a prime (19644937072121) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 10907793421 + ... + 10907795221.

Almost surely, 2^{19644937572121} is an apocalyptic number.

19644937572121 is the 4432261-st square number.

19644937572121 is the 2216131-st centered octagonal number.

It is an amenable number.

19644937572121 is a deficient number, since it is larger than the sum of its proper divisors (1096501154342).

19644937572121 is an frugal number, since it uses more digits than its factorization.

19644937572121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3862 (or 1931 counting only the distinct ones).

The product of its digits is 22861440, while the sum is 61.

The spelling of 19644937572121 in words is "nineteen trillion, six hundred forty-four billion, nine hundred thirty-seven million, five hundred seventy-two thousand, one hundred twenty-one".