21404123437 has 2 divisors, whose sum is σ = 21404123438. Its totient is φ = 21404123436.

The previous prime is 21404123381. The next prime is 21404123471. The reversal of 21404123437 is 73432140412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20744352841 + 659770596 = 144029^2 + 25686^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21404123437 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21404123399 and 21404123408.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21404123497) 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 as a sum of consecutive naturals, namely, 10702061718 + 10702061719.

It is an arithmetic number, because the mean of its divisors is an integer number (10702061719).

Almost surely, 2^21404123437 is an apocalyptic number.

It is an amenable number.

21404123437 is a deficient number, since it is larger than the sum of its proper divisors (1).

21404123437 is an equidigital number, since it uses as much as digits as its factorization.

21404123437 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16128, while the sum is 31.

Adding to 21404123437 its reverse (73432140412), we get a palindrome (94836263849).

The spelling of 21404123437 in words is "twenty-one billion, four hundred four million, one hundred twenty-three thousand, four hundred thirty-seven".