21635213 has 2 divisors, whose sum is σ = 21635214. Its totient is φ = 21635212.

The previous prime is 21635197. The next prime is 21635219. The reversal of 21635213 is 31253612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17623204 + 4012009 = 4198^2 + 2003^2 .

It is a cyclic number.

It is not a de Polignac number, because 21635213 - 2⁴ = 21635197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21635219) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10817606 + 10817607.

It is an arithmetic number, because the mean of its divisors is an integer number (10817607).

Almost surely, 2^21635213 is an apocalyptic number.

It is an amenable number.

21635213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21635213 is an equidigital number, since it uses as much as digits as its factorization.

21635213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1080, while the sum is 23.

The square root of 21635213 is about 4651.3667883752. The cubic root of 21635213 is about 278.6465851377.

Adding to 21635213 its reverse (31253612), we get a palindrome (52888825).

The spelling of 21635213 in words is "twenty-one million, six hundred thirty-five thousand, two hundred thirteen".