21943013 has 2 divisors, whose sum is σ = 21943014. Its totient is φ = 21943012.

The previous prime is 21943001. The next prime is 21943021. The reversal of 21943013 is 31034912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20638849 + 1304164 = 4543^2 + 1142^2 .

It is a cyclic number.

It is not a de Polignac number, because 21943013 - 2⁸ = 21942757 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21943013.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21943093) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10971506 + 10971507.

It is an arithmetic number, because the mean of its divisors is an integer number (10971507).

Almost surely, 2^21943013 is an apocalyptic number.

It is an amenable number.

21943013 is a deficient number, since it is larger than the sum of its proper divisors (1).

21943013 is an equidigital number, since it uses as much as digits as its factorization.

21943013 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648, while the sum is 23.

The square root of 21943013 is about 4684.3369861700. The cubic root of 21943013 is about 279.9617847505.

Adding to 21943013 its reverse (31034912), we get a palindrome (52977925).

The spelling of 21943013 in words is "twenty-one million, nine hundred forty-three thousand, thirteen".