21505044565 has 8 divisors (see below), whose sum is σ = 26638507008. Its totient is φ = 16649066640.

The previous prime is 21505044563. The next prime is 21505044571. The reversal of 21505044565 is 56544050512.

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

It is not a de Polignac number, because 21505044565 - 2¹ = 21505044563 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505044563) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 69370957 + ... + 69371266.

It is an arithmetic number, because the mean of its divisors is an integer number (3329813376).

Almost surely, 2^21505044565 is an apocalyptic number.

It is an amenable number.

21505044565 is a deficient number, since it is larger than the sum of its proper divisors (5133462443).

21505044565 is a wasteful number, since it uses less digits than its factorization.

21505044565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138742259.

The product of its (nonzero) digits is 120000, while the sum is 37.

The spelling of 21505044565 in words is "twenty-one billion, five hundred five million, forty-four thousand, five hundred sixty-five".