21431567 has 2 divisors, whose sum is σ = 21431568. Its totient is φ = 21431566.

The previous prime is 21431549. The next prime is 21431569. The reversal of 21431567 is 76513412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21431567 - 2¹⁴ = 21415183 is a prime.

Together with 21431569, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21431569) 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, 10715783 + 10715784.

It is an arithmetic number, because the mean of its divisors is an integer number (10715784).

Almost surely, 2^21431567 is an apocalyptic number.

21431567 is a deficient number, since it is larger than the sum of its proper divisors (1).

21431567 is an equidigital number, since it uses as much as digits as its factorization.

21431567 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5040, while the sum is 29.

The square root of 21431567 is about 4629.4240462502. The cubic root of 21431567 is about 277.7695543817.

Adding to 21431567 its reverse (76513412), we get a palindrome (97944979).

The spelling of 21431567 in words is "twenty-one million, four hundred thirty-one thousand, five hundred sixty-seven".