21405636173 has 16 divisors (see below), whose sum is σ = 23070712896. Its totient is φ = 19788476160.

The previous prime is 21405636097. The next prime is 21405636179. The reversal of 21405636173 is 37163650412.

It is a cyclic number.

It is not a de Polignac number, because 21405636173 - 2²⁸ = 21137200717 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21405636179) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 200258 + ... + 287948.

It is an arithmetic number, because the mean of its divisors is an integer number (1441919556).

Almost surely, 2^21405636173 is an apocalyptic number.

It is an amenable number.

21405636173 is a deficient number, since it is larger than the sum of its proper divisors (1665076723).

21405636173 is a wasteful number, since it uses less digits than its factorization.

21405636173 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87964.

The product of its (nonzero) digits is 90720, while the sum is 38.

The spelling of 21405636173 in words is "twenty-one billion, four hundred five million, six hundred thirty-six thousand, one hundred seventy-three".