21403312181 has 2 divisors, whose sum is σ = 21403312182. Its totient is φ = 21403312180.

The previous prime is 21403312127. The next prime is 21403312211. The reversal of 21403312181 is 18121330412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20487341956 + 915970225 = 143134^2 + 30265^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21403312181 is a prime.

It is a super-2 number, since 2×21403312181² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21403312181.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21403312121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10701656090 + 10701656091.

It is an arithmetic number, because the mean of its divisors is an integer number (10701656091).

Almost surely, 2^21403312181 is an apocalyptic number.

It is an amenable number.

21403312181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21403312181 is an equidigital number, since it uses as much as digits as its factorization.

21403312181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1152, while the sum is 26.

Adding to 21403312181 its reverse (18121330412), we get a palindrome (39524642593).

The spelling of 21403312181 in words is "twenty-one billion, four hundred three million, three hundred twelve thousand, one hundred eighty-one".