21727213 has 2 divisors, whose sum is σ = 21727214. Its totient is φ = 21727212.

The previous prime is 21727193. The next prime is 21727217. The reversal of 21727213 is 31272712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20958084 + 769129 = 4578^2 + 877^2 .

It is a cyclic number.

It is not a de Polignac number, because 21727213 - 2⁹ = 21726701 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21727217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10863606 + 10863607.

It is an arithmetic number, because the mean of its divisors is an integer number (10863607).

Almost surely, 2^21727213 is an apocalyptic number.

It is an amenable number.

21727213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21727213 is an equidigital number, since it uses as much as digits as its factorization.

21727213 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21727213 is about 4661.2458635004. The cubic root of 21727213 is about 279.0409920799.

Adding to 21727213 its reverse (31272712), we get a palindrome (52999925).

The spelling of 21727213 in words is "twenty-one million, seven hundred twenty-seven thousand, two hundred thirteen".