21003432421 has 2 divisors, whose sum is σ = 21003432422. Its totient is φ = 21003432420.

The previous prime is 21003432419. The next prime is 21003432581. The reversal of 21003432421 is 12423430012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20920440321 + 82992100 = 144639^2 + 9110^2 .

It is a cyclic number.

It is not a de Polignac number, because 21003432421 - 2¹ = 21003432419 is a prime.

It is a super-2 number, since 2×21003432421² (a number of 21 digits) contains 22 as substring.

Together with 21003432419, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21003432392 and 21003432401.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21003435421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501716210 + 10501716211.

It is an arithmetic number, because the mean of its divisors is an integer number (10501716211).

Almost surely, 2^21003432421 is an apocalyptic number.

It is an amenable number.

21003432421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21003432421 is an equidigital number, since it uses as much as digits as its factorization.

21003432421 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 22.

Adding to 21003432421 its reverse (12423430012), we get a palindrome (33426862433).

The spelling of 21003432421 in words is "twenty-one billion, three million, four hundred thirty-two thousand, four hundred twenty-one".