21565316861 has 8 divisors (see below), whose sum is σ = 23545209504. Its totient is φ = 19588659120.

The previous prime is 21565316831. The next prime is 21565316887. The reversal of 21565316861 is 16861356512.

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 21565316861 - 2³⁰ = 20491575037 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 (21565316821) 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 7 ways as a sum of consecutive naturals, for example, 794771 + ... + 821456.

It is an arithmetic number, because the mean of its divisors is an integer number (2943151188).

Almost surely, 2^21565316861 is an apocalyptic number.

It is an amenable number.

21565316861 is a deficient number, since it is larger than the sum of its proper divisors (1979892643).

21565316861 is a wasteful number, since it uses less digits than its factorization.

21565316861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1617451.

The product of its digits is 259200, while the sum is 44.

The spelling of 21565316861 in words is "twenty-one billion, five hundred sixty-five million, three hundred sixteen thousand, eight hundred sixty-one".