21203771 has 2 divisors, whose sum is σ = 21203772. Its totient is φ = 21203770.

The previous prime is 21203759. The next prime is 21203789. The reversal of 21203771 is 17730212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21203771 - 2¹⁰ = 21202747 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21203711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10601885 + 10601886.

It is an arithmetic number, because the mean of its divisors is an integer number (10601886).

Almost surely, 2^21203771 is an apocalyptic number.

21203771 is a deficient number, since it is larger than the sum of its proper divisors (1).

21203771 is an equidigital number, since it uses as much as digits as its factorization.

21203771 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 588, while the sum is 23.

The square root of 21203771 is about 4604.7552595116. The cubic root of 21203771 is about 276.7819098614.

Adding to 21203771 its reverse (17730212), we get a palindrome (38933983).

The spelling of 21203771 in words is "twenty-one million, two hundred three thousand, seven hundred seventy-one".