21207533 has 2 divisors, whose sum is σ = 21207534. Its totient is φ = 21207532.

The previous prime is 21207509. The next prime is 21207539. The reversal of 21207533 is 33570212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16176484 + 5031049 = 4022^2 + 2243^2 .

It is a cyclic number.

It is not a de Polignac number, because 21207533 - 2⁶ = 21207469 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21207499 and 21207508.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21207539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10603766 + 10603767.

It is an arithmetic number, because the mean of its divisors is an integer number (10603767).

Almost surely, 2^21207533 is an apocalyptic number.

It is an amenable number.

21207533 is a deficient number, since it is larger than the sum of its proper divisors (1).

21207533 is an equidigital number, since it uses as much as digits as its factorization.

21207533 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1260, while the sum is 23.

The square root of 21207533 is about 4605.1637321598. The cubic root of 21207533 is about 276.7982778928.

Adding to 21207533 its reverse (33570212), we get a palindrome (54777745).

The spelling of 21207533 in words is "twenty-one million, two hundred seven thousand, five hundred thirty-three".