21356205707173 has 4 divisors (see below), whose sum is σ = 21369047684608. Its totient is φ = 21343363729740.

The previous prime is 21356205707153. The next prime is 21356205707203. The reversal of 21356205707173 is 37170750265312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21356205707173 - 2⁵ = 21356205707141 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 (21356205707153) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6420986223 + ... + 6420989548.

It is an arithmetic number, because the mean of its divisors is an integer number (5342261921152).

Almost surely, 2^{21356205707173} is an apocalyptic number.

It is an amenable number.

21356205707173 is a deficient number, since it is larger than the sum of its proper divisors (12841977435).

21356205707173 is a wasteful number, since it uses less digits than its factorization.

21356205707173 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12841977434.

The product of its (nonzero) digits is 1852200, while the sum is 49.

The spelling of 21356205707173 in words is "twenty-one trillion, three hundred fifty-six billion, two hundred five million, seven hundred seven thousand, one hundred seventy-three".