21608173 has 4 divisors (see below), whose sum is σ = 22879260. Its totient is φ = 20337088.

The previous prime is 21608123. The next prime is 21608227. The reversal of 21608173 is 37180612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6538249 + 15069924 = 2557^2 + 3882^2 .

It is a cyclic number.

It is not a de Polignac number, because 21608173 - 2⁹ = 21607661 is a prime.

It is a Duffinian number.

It is a plaindrome in base 8.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21608113) 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, 635518 + ... + 635551.

It is an arithmetic number, because the mean of its divisors is an integer number (5719815).

Almost surely, 2^21608173 is an apocalyptic number.

It is an amenable number.

21608173 is a deficient number, since it is larger than the sum of its proper divisors (1271087).

21608173 is a wasteful number, since it uses less digits than its factorization.

21608173 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1271086.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21608173 is about 4648.4592070922. The cubic root of 21608173 is about 278.5304512407.

Adding to 21608173 its reverse (37180612), we get a palindrome (58788785).

The spelling of 21608173 in words is "twenty-one million, six hundred eight thousand, one hundred seventy-three".