21731263 has 2 divisors, whose sum is σ = 21731264. Its totient is φ = 21731262.

The previous prime is 21731257. The next prime is 21731273. The reversal of 21731263 is 36213712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21731263 - 2¹⁷ = 21600191 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21731243) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10865631 + 10865632.

It is an arithmetic number, because the mean of its divisors is an integer number (10865632).

Almost surely, 2^21731263 is an apocalyptic number.

21731263 is a deficient number, since it is larger than the sum of its proper divisors (1).

21731263 is an equidigital number, since it uses as much as digits as its factorization.

21731263 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1512, while the sum is 25.

The square root of 21731263 is about 4661.6802764668. The cubic root of 21731263 is about 279.0583289531.

Adding to 21731263 its reverse (36213712), we get a palindrome (57944975).

The spelling of 21731263 in words is "twenty-one million, seven hundred thirty-one thousand, two hundred sixty-three".