21324611781 has 18 divisors (see below), whose sum is σ = 33856984070. Its totient is φ = 12924006480.

The previous prime is 21324611773. The next prime is 21324611801. The reversal of 21324611781 is 18711642312.

21324611781 is a `hidden beast` number, since 2 + 1 + 32 + 4 + 611 + 7 + 8 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 12774650625 + 8549961156 = 113025^2 + 92466^2 .

It is not a de Polignac number, because 21324611781 - 2³ = 21324611773 is a prime.

It is a super-2 number, since 2×21324611781² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21324611701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 9789826 + ... + 9792003.

Almost surely, 2^21324611781 is an apocalyptic number.

It is an amenable number.

21324611781 is a deficient number, since it is larger than the sum of its proper divisors (12532372289).

21324611781 is a wasteful number, since it uses less digits than its factorization.

21324611781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19581857 (or 19581843 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The spelling of 21324611781 in words is "twenty-one billion, three hundred twenty-four million, six hundred eleven thousand, seven hundred eighty-one".