21007213 has 2 divisors, whose sum is σ = 21007214. Its totient is φ = 21007212.

The previous prime is 21007201. The next prime is 21007229. The reversal of 21007213 is 31270012.

It is a happy number.

It is an a-pointer prime, because the next prime (21007229) can be obtained adding 21007213 to its sum of digits (16).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19474569 + 1532644 = 4413^2 + 1238^2 .

It is a cyclic number.

It is not a de Polignac number, because 21007213 - 2¹³ = 20999021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21007253) 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, 10503606 + 10503607.

It is an arithmetic number, because the mean of its divisors is an integer number (10503607).

Almost surely, 2^21007213 is an apocalyptic number.

It is an amenable number.

21007213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21007213 is an equidigital number, since it uses as much as digits as its factorization.

21007213 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 84, while the sum is 16.

The square root of 21007213 is about 4583.3626302094. The cubic root of 21007213 is about 275.9240015145.

Adding to 21007213 its reverse (31270012), we get a palindrome (52277225).

The spelling of 21007213 in words is "twenty-one million, seven thousand, two hundred thirteen".