21065173 has 8 divisors (see below), whose sum is σ = 21785400. Its totient is φ = 20352960.

The previous prime is 21065153. The next prime is 21065179. The reversal of 21065173 is 37156012.

It can be written as a sum of positive squares in 4 ways, for example, as 7360369 + 13704804 = 2713^2 + 3702^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21065173 - 2²¹ = 18968021 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 (21065179) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3603 + ... + 7423.

It is an arithmetic number, because the mean of its divisors is an integer number (2723175).

Almost surely, 2^21065173 is an apocalyptic number.

It is an amenable number.

21065173 is a deficient number, since it is larger than the sum of its proper divisors (720227).

21065173 is a wasteful number, since it uses less digits than its factorization.

21065173 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4007.

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 21065173 is about 4589.6811436090. The cubic root of 21065173 is about 276.1775314097.

The spelling of 21065173 in words is "twenty-one million, sixty-five thousand, one hundred seventy-three".