21203123 has 2 divisors, whose sum is σ = 21203124. Its totient is φ = 21203122.

The previous prime is 21203113. The next prime is 21203129. The reversal of 21203123 is 32130212.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21203123 - 2¹² = 21199027 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21203098 and 21203107.

It is not a weakly prime, because it can be changed into another prime (21203129) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10601561 + 10601562.

It is an arithmetic number, because the mean of its divisors is an integer number (10601562).

Almost surely, 2^21203123 is an apocalyptic number.

21203123 is a deficient number, since it is larger than the sum of its proper divisors (1).

21203123 is an equidigital number, since it uses as much as digits as its factorization.

21203123 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72, while the sum is 14.

The square root of 21203123 is about 4604.6848969283. The cubic root of 21203123 is about 276.7790902921.

Adding to 21203123 its reverse (32130212), we get a palindrome (53333335).

The spelling of 21203123 in words is "twenty-one million, two hundred three thousand, one hundred twenty-three".