21404123281 has 2 divisors, whose sum is σ = 21404123282. Its totient is φ = 21404123280.

The previous prime is 21404123261. The next prime is 21404123317. The reversal of 21404123281 is 18232140412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21032250625 + 371872656 = 145025^2 + 19284^2 .

It is a cyclic number.

It is not a de Polignac number, because 21404123281 - 2²³ = 21395734673 is a prime.

It is a super-2 number, since 2×21404123281² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21404123261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702061640 + 10702061641.

It is an arithmetic number, because the mean of its divisors is an integer number (10702061641).

Almost surely, 2^21404123281 is an apocalyptic number.

It is an amenable number.

21404123281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21404123281 is an equidigital number, since it uses as much as digits as its factorization.

21404123281 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3072, while the sum is 28.

Adding to 21404123281 its reverse (18232140412), we get a palindrome (39636263693).

The spelling of 21404123281 in words is "twenty-one billion, four hundred four million, one hundred twenty-three thousand, two hundred eighty-one".