21078173 has 4 divisors (see below), whose sum is σ = 21094080. Its totient is φ = 21062268.

The previous prime is 21078149. The next prime is 21078179. The reversal of 21078173 is 37187012.

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 21078173 - 2¹² = 21074077 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 (21078179) 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, 5765 + ... + 8682.

It is an arithmetic number, because the mean of its divisors is an integer number (5273520).

Almost surely, 2^21078173 is an apocalyptic number.

It is an amenable number.

21078173 is a deficient number, since it is larger than the sum of its proper divisors (15907).

21078173 is a wasteful number, since it uses less digits than its factorization.

21078173 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15906.

The product of its (nonzero) digits is 2352, while the sum is 29.

The square root of 21078173 is about 4591.0971455634. The cubic root of 21078173 is about 276.2343324243.

The spelling of 21078173 in words is "twenty-one million, seventy-eight thousand, one hundred seventy-three".