21722173 has 4 divisors (see below), whose sum is σ = 23696928. Its totient is φ = 19747420.

The previous prime is 21722167. The next prime is 21722201. The reversal of 21722173 is 37122712.

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 de Polignac number, because none of the positive numbers 2^k-21722173 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 (21722153) 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, 987361 + ... + 987382.

It is an arithmetic number, because the mean of its divisors is an integer number (5924232).

Almost surely, 2^21722173 is an apocalyptic number.

It is an amenable number.

21722173 is a deficient number, since it is larger than the sum of its proper divisors (1974755).

21722173 is a wasteful number, since it uses less digits than its factorization.

21722173 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1974754.

The product of its digits is 1176, while the sum is 25.

The square root of 21722173 is about 4660.7052041510. The cubic root of 21722173 is about 279.0194142954.

Adding to 21722173 its reverse (37122712), we get a palindrome (58844885).

The spelling of 21722173 in words is "twenty-one million, seven hundred twenty-two thousand, one hundred seventy-three".