21236431 has 2 divisors, whose sum is σ = 21236432. Its totient is φ = 21236430.

The previous prime is 21236419. The next prime is 21236447. The reversal of 21236431 is 13463212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21236431 - 2⁵ = 21236399 is a prime.

It is a super-2 number, since 2×21236431² = 901972003235522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21236491) 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, 10618215 + 10618216.

It is an arithmetic number, because the mean of its divisors is an integer number (10618216).

Almost surely, 2^21236431 is an apocalyptic number.

21236431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21236431 is an equidigital number, since it uses as much as digits as its factorization.

21236431 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 22.

The square root of 21236431 is about 4608.3002289347. The cubic root of 21236431 is about 276.9239452865.

Adding to 21236431 its reverse (13463212), we get a palindrome (34699643).

The spelling of 21236431 in words is "twenty-one million, two hundred thirty-six thousand, four hundred thirty-one".