21686528561 has 8 divisors (see below), whose sum is σ = 22315098624. Its totient is φ = 21062702880.

The previous prime is 21686528551. The next prime is 21686528623. The reversal of 21686528561 is 16582568612.

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 21686528561 - 2¹⁰ = 21686527537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21686528551) 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, 1176821 + ... + 1195106.

It is an arithmetic number, because the mean of its divisors is an integer number (2789387328).

Almost surely, 2^21686528561 is an apocalyptic number.

It is an amenable number.

21686528561 is a deficient number, since it is larger than the sum of its proper divisors (628570063).

21686528561 is a wasteful number, since it uses less digits than its factorization.

21686528561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2372191.

The product of its digits is 1382400, while the sum is 50.

The spelling of 21686528561 in words is "twenty-one billion, six hundred eighty-six million, five hundred twenty-eight thousand, five hundred sixty-one".