21123287 has 2 divisors, whose sum is σ = 21123288. Its totient is φ = 21123286.

The previous prime is 21123211. The next prime is 21123293. The reversal of 21123287 is 78232112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21123287 - 2¹⁸ = 20861143 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21123187) 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, 10561643 + 10561644.

It is an arithmetic number, because the mean of its divisors is an integer number (10561644).

Almost surely, 2^21123287 is an apocalyptic number.

21123287 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123287 is an equidigital number, since it uses as much as digits as its factorization.

21123287 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1344, while the sum is 26.

The square root of 21123287 is about 4596.0077241014. The cubic root of 21123287 is about 276.4312684573.

Adding to 21123287 its reverse (78232112), we get a palindrome (99355399).

The spelling of 21123287 in words is "twenty-one million, one hundred twenty-three thousand, two hundred eighty-seven".