21307229 has 2 divisors, whose sum is σ = 21307230. Its totient is φ = 21307228.

The previous prime is 21307193. The next prime is 21307243. The reversal of 21307229 is 92270312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15784729 + 5522500 = 3973^2 + 2350^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21307229 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21307198 and 21307207.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21307529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10653614 + 10653615.

It is an arithmetic number, because the mean of its divisors is an integer number (10653615).

Almost surely, 2^21307229 is an apocalyptic number.

It is an amenable number.

21307229 is a deficient number, since it is larger than the sum of its proper divisors (1).

21307229 is an equidigital number, since it uses as much as digits as its factorization.

21307229 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1512, while the sum is 26.

The square root of 21307229 is about 4615.9754115463. The cubic root of 21307229 is about 277.2313402317.

The spelling of 21307229 in words is "twenty-one million, three hundred seven thousand, two hundred twenty-nine".