21304439437 has 2 divisors, whose sum is σ = 21304439438. Its totient is φ = 21304439436.

The previous prime is 21304439381. The next prime is 21304439449. The reversal of 21304439437 is 73493440312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13079581956 + 8224857481 = 114366^2 + 90691^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21304439437 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21304439437.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21304430437) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10652219718 + 10652219719.

It is an arithmetic number, because the mean of its divisors is an integer number (10652219719).

Almost surely, 2^21304439437 is an apocalyptic number.

It is an amenable number.

21304439437 is a deficient number, since it is larger than the sum of its proper divisors (1).

21304439437 is an equidigital number, since it uses as much as digits as its factorization.

21304439437 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 217728, while the sum is 40.

Adding to 21304439437 its reverse (73493440312), we get a palindrome (94797879749).

The spelling of 21304439437 in words is "twenty-one billion, three hundred four million, four hundred thirty-nine thousand, four hundred thirty-seven".