21665386645 has 8 divisors (see below), whose sum is σ = 29712530304. Its totient is φ = 14856265104.

The previous prime is 21665386627. The next prime is 21665386651. The reversal of 21665386645 is 54668356612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21665386645 - 2⁹ = 21665386133 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21665386592 and 21665386601.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 309505489 + ... + 309505558.

It is an arithmetic number, because the mean of its divisors is an integer number (3714066288).

Almost surely, 2^21665386645 is an apocalyptic number.

It is an amenable number.

21665386645 is a deficient number, since it is larger than the sum of its proper divisors (8047143659).

21665386645 is an equidigital number, since it uses as much as digits as its factorization.

21665386645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 619011059.

The product of its digits is 6220800, while the sum is 52.

The spelling of 21665386645 in words is "twenty-one billion, six hundred sixty-five million, three hundred eighty-six thousand, six hundred forty-five".