21404420281 has 2 divisors, whose sum is σ = 21404420282. Its totient is φ = 21404420280.

The previous prime is 21404420269. The next prime is 21404420309. The reversal of 21404420281 is 18202440412.

It is an a-pointer prime, because the next prime (21404420309) can be obtained adding 21404420281 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20619524025 + 784896256 = 143595^2 + 28016^2 .

It is a cyclic number.

It is not a de Polignac number, because 21404420281 - 2¹⁵ = 21404387513 is a prime.

It is a super-2 number, since 2×21404420281² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21404420221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702210140 + 10702210141.

It is an arithmetic number, because the mean of its divisors is an integer number (10702210141).

Almost surely, 2^21404420281 is an apocalyptic number.

It is an amenable number.

21404420281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21404420281 is an equidigital number, since it uses as much as digits as its factorization.

21404420281 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4096, while the sum is 28.

Adding to 21404420281 its reverse (18202440412), we get a palindrome (39606860693).

The spelling of 21404420281 in words is "twenty-one billion, four hundred four million, four hundred twenty thousand, two hundred eighty-one".