21543031 has 2 divisors, whose sum is σ = 21543032. Its totient is φ = 21543030.

The previous prime is 21543013. The next prime is 21543077. The reversal of 21543031 is 13034512.

Together with previous prime (21543013) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21543031 - 2¹¹ = 21540983 is a prime.

It is a super-2 number, since 2×21543031² = 928204369333922, which contains 22 as substring.

It is equal to p_1362124 and since 21543031 and 1362124 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21543001) 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, 10771515 + 10771516.

It is an arithmetic number, because the mean of its divisors is an integer number (10771516).

Almost surely, 2^21543031 is an apocalyptic number.

21543031 is a deficient number, since it is larger than the sum of its proper divisors (1).

21543031 is an equidigital number, since it uses as much as digits as its factorization.

21543031 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 21543031 is about 4641.4470803834. The cubic root of 21543031 is about 278.2502749366.

Adding to 21543031 its reverse (13034512), we get a palindrome (34577543).

The spelling of 21543031 in words is "twenty-one million, five hundred forty-three thousand, thirty-one".