21943213 has 2 divisors, whose sum is σ = 21943214. Its totient is φ = 21943212.

The previous prime is 21943211. The next prime is 21943231. The reversal of 21943213 is 31234912.

Together with next prime (21943231) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18550249 + 3392964 = 4307^2 + 1842^2 .

It is a cyclic number.

It is not a de Polignac number, because 21943213 - 2¹ = 21943211 is a prime.

Together with 21943211, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21943211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10971606 + 10971607.

It is an arithmetic number, because the mean of its divisors is an integer number (10971607).

Almost surely, 2^21943213 is an apocalyptic number.

It is an amenable number.

21943213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21943213 is an equidigital number, since it uses as much as digits as its factorization.

21943213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296, while the sum is 25.

The square root of 21943213 is about 4684.3583338596. The cubic root of 21943213 is about 279.9626353202.

The spelling of 21943213 in words is "twenty-one million, nine hundred forty-three thousand, two hundred thirteen".