21312671 has 2 divisors, whose sum is σ = 21312672. Its totient is φ = 21312670.

The previous prime is 21312647. The next prime is 21312673. The reversal of 21312671 is 17621312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21312671 - 2¹⁸ = 21050527 is a prime.

Together with 21312673, 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 (21312673) 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, 10656335 + 10656336.

It is an arithmetic number, because the mean of its divisors is an integer number (10656336).

Almost surely, 2^21312671 is an apocalyptic number.

21312671 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312671 is an equidigital number, since it uses as much as digits as its factorization.

21312671 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 504, while the sum is 23.

The square root of 21312671 is about 4616.5648484560. The cubic root of 21312671 is about 277.2549404306.

Adding to 21312671 its reverse (17621312), we get a palindrome (38933983).

The spelling of 21312671 in words is "twenty-one million, three hundred twelve thousand, six hundred seventy-one".