21231112681 has 3 divisors (see below), whose sum is σ = 21231258391. Its totient is φ = 21230966972.

The previous prime is 21231112667. The next prime is 21231112717. The reversal of 21231112681 is 18621113212.

The square root of 21231112681 is 145709.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 3801832281 + 17429280400 = 61659^2 + 132020^2 .

It is not a de Polignac number, because 21231112681 - 2²¹ = 21229015529 is a prime.

It is a super-2 number, since 2×21231112681² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21231112081) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 72855 + ... + 218563.

Almost surely, 2^21231112681 is an apocalyptic number.

21231112681 is the 145709-th square number.

21231112681 is the 72855-th centered octagonal number.

It is an amenable number.

21231112681 is a deficient number, since it is larger than the sum of its proper divisors (145710).

21231112681 is an frugal number, since it uses more digits than its factorization.

21231112681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291418 (or 145709 counting only the distinct ones).

The product of its digits is 1152, while the sum is 28.

Adding to 21231112681 its reverse (18621113212), we get a palindrome (39852225893).

The spelling of 21231112681 in words is "twenty-one billion, two hundred thirty-one million, one hundred twelve thousand, six hundred eighty-one".