21404124421 has 2 divisors, whose sum is σ = 21404124422. Its totient is φ = 21404124420.

The previous prime is 21404124403. The next prime is 21404124449. The reversal of 21404124421 is 12442140412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11834393796 + 9569730625 = 108786^2 + 97825^2 .

It is a cyclic number.

It is not a de Polignac number, because 21404124421 - 2²³ = 21395735813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21404164421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702062210 + 10702062211.

It is an arithmetic number, because the mean of its divisors is an integer number (10702062211).

Almost surely, 2^21404124421 is an apocalyptic number.

It is an amenable number.

21404124421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21404124421 is an equidigital number, since it uses as much as digits as its factorization.

21404124421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2048, while the sum is 25.

Adding to 21404124421 its reverse (12442140412), we get a palindrome (33846264833).

The spelling of 21404124421 in words is "twenty-one billion, four hundred four million, one hundred twenty-four thousand, four hundred twenty-one".