21643406409 has 4 divisors (see below), whose sum is σ = 28857875216. Its totient is φ = 14428937604.

The previous prime is 21643406399. The next prime is 21643406413. The reversal of 21643406409 is 90460434612.

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 not a de Polignac number, because 21643406409 - 2⁸ = 21643406153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21643406459) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3607234399 + ... + 3607234404.

It is an arithmetic number, because the mean of its divisors is an integer number (7214468804).

Almost surely, 2^21643406409 is an apocalyptic number.

It is an amenable number.

21643406409 is a deficient number, since it is larger than the sum of its proper divisors (7214468807).

21643406409 is an equidigital number, since it uses as much as digits as its factorization.

21643406409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7214468806.

The product of its (nonzero) digits is 124416, while the sum is 39.

The spelling of 21643406409 in words is "twenty-one billion, six hundred forty-three million, four hundred six thousand, four hundred nine".