21007253 has 2 divisors, whose sum is σ = 21007254. Its totient is φ = 21007252.

The previous prime is 21007249. The next prime is 21007289. The reversal of 21007253 is 35270012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21003889 + 3364 = 4583^2 + 58^2 .

It is a cyclic number.

It is not a de Polignac number, because 21007253 - 2² = 21007249 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21007213) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10503626 + 10503627.

It is an arithmetic number, because the mean of its divisors is an integer number (10503627).

Almost surely, 2^21007253 is an apocalyptic number.

It is an amenable number.

21007253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21007253 is an equidigital number, since it uses as much as digits as its factorization.

21007253 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 21007253 is about 4583.3669938158. The cubic root of 21007253 is about 275.9241766441.

Adding to 21007253 its reverse (35270012), we get a palindrome (56277265).

The spelling of 21007253 in words is "twenty-one million, seven thousand, two hundred fifty-three".