21304709 has 2 divisors, whose sum is σ = 21304710. Its totient is φ = 21304708.

The previous prime is 21304697. The next prime is 21304721. The reversal of 21304709 is 90740312.

It is a balanced prime because it is at equal distance from previous prime (21304697) and next prime (21304721).

It can be written as a sum of positive squares in only one way, i.e., 18515809 + 2788900 = 4303^2 + 1670^2 .

It is a cyclic number.

It is not a de Polignac number, because 21304709 - 2¹⁶ = 21239173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21304109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10652354 + 10652355.

It is an arithmetic number, because the mean of its divisors is an integer number (10652355).

Almost surely, 2^21304709 is an apocalyptic number.

It is an amenable number.

21304709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21304709 is an equidigital number, since it uses as much as digits as its factorization.

21304709 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 21304709 is about 4615.7024384161. The cubic root of 21304709 is about 277.2204104432.

The spelling of 21304709 in words is "twenty-one million, three hundred four thousand, seven hundred nine".