21041565805 has 32 divisors (see below), whose sum is σ = 28811510784. Its totient is φ = 14614311936.

The previous prime is 21041565793. The next prime is 21041565833. The reversal of 21041565805 is 50856514012.

It is not a de Polignac number, because 21041565805 - 2⁵ = 21041565773 is a prime.

It is a super-2 number, since 2×21041565805² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 1836324 + ... + 1847746.

It is an arithmetic number, because the mean of its divisors is an integer number (900359712).

Almost surely, 2^21041565805 is an apocalyptic number.

It is an amenable number.

21041565805 is a deficient number, since it is larger than the sum of its proper divisors (7769944979).

21041565805 is a wasteful number, since it uses less digits than its factorization.

21041565805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13125.

The product of its (nonzero) digits is 48000, while the sum is 37.

The spelling of 21041565805 in words is "twenty-one billion, forty-one million, five hundred sixty-five thousand, eight hundred five".