21043481 has 2 divisors, whose sum is σ = 21043482. Its totient is φ = 21043480.

The previous prime is 21043457. The next prime is 21043483. The reversal of 21043481 is 18434012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20976400 + 67081 = 4580^2 + 259^2 .

It is a cyclic number.

It is not a de Polignac number, because 21043481 - 2¹⁰ = 21042457 is a prime.

It is a super-2 number, since 2×21043481² = 885656185194722, which contains 22 as substring.

Together with 21043483, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21043483) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521740 + 10521741.

It is an arithmetic number, because the mean of its divisors is an integer number (10521741).

Almost surely, 2^21043481 is an apocalyptic number.

It is an amenable number.

21043481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21043481 is an equidigital number, since it uses as much as digits as its factorization.

21043481 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 21043481 is about 4587.3174078104. The cubic root of 21043481 is about 276.0827003101.

Adding to 21043481 its reverse (18434012), we get a palindrome (39477493).

The spelling of 21043481 in words is "twenty-one million, forty-three thousand, four hundred eighty-one".