21938645689 has 9 divisors (see below), whose sum is σ = 22254260013. Its totient is φ = 21627451872.

The previous prime is 21938645593. The next prime is 21938645731. The reversal of 21938645689 is 98654683912.

The square root of 21938645689 is 148117.

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

It can be written as a sum of positive squares in 4 ways, for example, as 10509325225 + 11429320464 = 102515^2 + 106908^2 .

It is not a de Polignac number, because 21938645689 - 2⁹ = 21938645177 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21938645189) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 10811527 + ... + 10813555.

It is an arithmetic number, because the mean of its divisors is an integer number (2472695557).

Almost surely, 2^21938645689 is an apocalyptic number.

21938645689 is the 148117-th square number.

21938645689 is the 74059-th centered octagonal number.

It is an amenable number.

21938645689 is a deficient number, since it is larger than the sum of its proper divisors (315614324).

21938645689 is an frugal number, since it uses more digits than its factorization.

21938645689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4204 (or 2102 counting only the distinct ones).

The product of its digits is 22394880, while the sum is 61.

The spelling of 21938645689 in words is "twenty-one billion, nine hundred thirty-eight million, six hundred forty-five thousand, six hundred eighty-nine".