21515233 has 2 divisors, whose sum is σ = 21515234. Its totient is φ = 21515232.

The previous prime is 21515227. The next prime is 21515257. The reversal of 21515233 is 33251512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18249984 + 3265249 = 4272^2 + 1807^2 .

It is a cyclic number.

It is not a de Polignac number, because 21515233 - 2⁹ = 21514721 is a prime.

It is not a weakly prime, because it can be changed into another prime (21515203) 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, 10757616 + 10757617.

It is an arithmetic number, because the mean of its divisors is an integer number (10757617).

Almost surely, 2^21515233 is an apocalyptic number.

It is an amenable number.

21515233 is a deficient number, since it is larger than the sum of its proper divisors (1).

21515233 is an equidigital number, since it uses as much as digits as its factorization.

21515233 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 900, while the sum is 22.

The square root of 21515233 is about 4638.4515735318. The cubic root of 21515233 is about 278.1305435582.

Adding to 21515233 its reverse (33251512), we get a palindrome (54766745).

The spelling of 21515233 in words is "twenty-one million, five hundred fifteen thousand, two hundred thirty-three".