21175321 has 4 divisors (see below), whose sum is σ = 21369700. Its totient is φ = 20980944.

The previous prime is 21175309. The next prime is 21175331. The reversal of 21175321 is 12357112.

It is a happy number.

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 8294400 + 12880921 = 2880^2 + 3589^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21175321 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21175292 and 21175301.

It is not an unprimeable number, because it can be changed into a prime (21175331) 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, 97026 + ... + 97243.

It is an arithmetic number, because the mean of its divisors is an integer number (5342425).

Almost surely, 2^21175321 is an apocalyptic number.

It is an amenable number.

21175321 is a deficient number, since it is larger than the sum of its proper divisors (194379).

21175321 is a wasteful number, since it uses less digits than its factorization.

21175321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 194378.

The product of its digits is 420, while the sum is 22.

The square root of 21175321 is about 4601.6650247492. The cubic root of 21175321 is about 276.6580644412.

The spelling of 21175321 in words is "twenty-one million, one hundred seventy-five thousand, three hundred twenty-one".