21203431 has 2 divisors, whose sum is σ = 21203432. Its totient is φ = 21203430.

The previous prime is 21203419. The next prime is 21203459. The reversal of 21203431 is 13430212.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21203431 - 2⁹ = 21202919 is a prime.

It is a super-2 number, since 2×21203431² = 899170972343522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21203731) 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, 10601715 + 10601716.

It is an arithmetic number, because the mean of its divisors is an integer number (10601716).

Almost surely, 2^21203431 is an apocalyptic number.

21203431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21203431 is an equidigital number, since it uses as much as digits as its factorization.

21203431 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21203431 is about 4604.7183410063. The cubic root of 21203431 is about 276.7804304649.

Adding to 21203431 its reverse (13430212), we get a palindrome (34633643).

The spelling of 21203431 in words is "twenty-one million, two hundred three thousand, four hundred thirty-one".