21606394643 has 4 divisors (see below), whose sum is σ = 21664321008. Its totient is φ = 21548468280.

The previous prime is 21606394637. The next prime is 21606394699. The reversal of 21606394643 is 34649360612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21606394643 - 2⁸ = 21606394387 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21606394594 and 21606394603.

It is not an unprimeable number, because it can be changed into a prime (21606324643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28962623 + ... + 28963368.

It is an arithmetic number, because the mean of its divisors is an integer number (5416080252).

Almost surely, 2^21606394643 is an apocalyptic number.

21606394643 is a deficient number, since it is larger than the sum of its proper divisors (57926365).

21606394643 is an equidigital number, since it uses as much as digits as its factorization.

21606394643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57926364.

The product of its (nonzero) digits is 559872, while the sum is 44.

The spelling of 21606394643 in words is "twenty-one billion, six hundred six million, three hundred ninety-four thousand, six hundred forty-three".