21170213 has 2 divisors, whose sum is σ = 21170214. Its totient is φ = 21170212.

The previous prime is 21170209. The next prime is 21170221. The reversal of 21170213 is 31207112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15108769 + 6061444 = 3887^2 + 2462^2 .

It is a cyclic number.

It is not a de Polignac number, because 21170213 - 2² = 21170209 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21170191 and 21170200.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21170273) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10585106 + 10585107.

It is an arithmetic number, because the mean of its divisors is an integer number (10585107).

Almost surely, 2^21170213 is an apocalyptic number.

It is an amenable number.

21170213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21170213 is an equidigital number, since it uses as much as digits as its factorization.

21170213 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 21170213 is about 4601.1099747778. The cubic root of 21170213 is about 276.6358171115.

Adding to 21170213 its reverse (31207112), we get a palindrome (52377325).

The spelling of 21170213 in words is "twenty-one million, one hundred seventy thousand, two hundred thirteen".