21506333 has 2 divisors, whose sum is σ = 21506334. Its totient is φ = 21506332.

The previous prime is 21506323. The next prime is 21506339. The reversal of 21506333 is 33360512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17960644 + 3545689 = 4238^2 + 1883^2 .

It is a cyclic number.

It is not a de Polignac number, because 21506333 - 2⁶ = 21506269 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21506299 and 21506308.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21506339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753166 + 10753167.

It is an arithmetic number, because the mean of its divisors is an integer number (10753167).

Almost surely, 2^21506333 is an apocalyptic number.

It is an amenable number.

21506333 is a deficient number, since it is larger than the sum of its proper divisors (1).

21506333 is an equidigital number, since it uses as much as digits as its factorization.

21506333 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1620, while the sum is 23.

The square root of 21506333 is about 4637.4921024192. The cubic root of 21506333 is about 278.0921877379.

Adding to 21506333 its reverse (33360512), we get a palindrome (54866845).

The spelling of 21506333 in words is "twenty-one million, five hundred six thousand, three hundred thirty-three".