21404404021 has 24 divisors (see below), whose sum is σ = 28956513152. Its totient is φ = 15395767200.

The previous prime is 21404403983. The next prime is 21404404033. The reversal of 21404404021 is 12040440412.

It is not a de Polignac number, because 21404404021 - 2⁷ = 21404403893 is a prime.

It is a super-2 number, since 2×21404404021² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21404403983 and 21404404001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404404051) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 960945 + ... + 982966.

Almost surely, 2^21404404021 is an apocalyptic number.

It is an amenable number.

21404404021 is a deficient number, since it is larger than the sum of its proper divisors (7552109131).

21404404021 is a wasteful number, since it uses less digits than its factorization.

21404404021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1943953 (or 1943942 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 22.

Adding to 21404404021 its reverse (12040440412), we get a palindrome (33444844433).

The spelling of 21404404021 in words is "twenty-one billion, four hundred four million, four hundred four thousand, twenty-one".