21043402409 has 4 divisors (see below), whose sum is σ = 21045824640. Its totient is φ = 21040980180.

The previous prime is 21043402403. The next prime is 21043402433. The reversal of 21043402409 is 90420434012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21043402409 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21043402403) 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 in 3 ways as a sum of consecutive naturals, for example, 1198037 + ... + 1215474.

It is an arithmetic number, because the mean of its divisors is an integer number (5261456160).

Almost surely, 2^21043402409 is an apocalyptic number.

It is an amenable number.

21043402409 is a deficient number, since it is larger than the sum of its proper divisors (2422231).

21043402409 is an equidigital number, since it uses as much as digits as its factorization.

21043402409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2422230.

The product of its (nonzero) digits is 6912, while the sum is 29.

The spelling of 21043402409 in words is "twenty-one billion, forty-three million, four hundred two thousand, four hundred nine".