21234281 has 2 divisors, whose sum is σ = 21234282. Its totient is φ = 21234280.

The previous prime is 21234211. The next prime is 21234299. The reversal of 21234281 is 18243212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13808656 + 7425625 = 3716^2 + 2725^2 .

It is a cyclic number.

It is not a de Polignac number, because 21234281 - 2¹⁸ = 20972137 is a prime.

It is a super-2 number, since 2×21234281² = 901789379173922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21234211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10617140 + 10617141.

It is an arithmetic number, because the mean of its divisors is an integer number (10617141).

Almost surely, 2^21234281 is an apocalyptic number.

It is an amenable number.

21234281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21234281 is an equidigital number, since it uses as much as digits as its factorization.

21234281 is an evil number, because the sum of its binary digits is even.

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

The square root of 21234281 is about 4608.0669482984. The cubic root of 21234281 is about 276.9145996079.

Adding to 21234281 its reverse (18243212), we get a palindrome (39477493).

The spelling of 21234281 in words is "twenty-one million, two hundred thirty-four thousand, two hundred eighty-one".