20656709 has 2 divisors, whose sum is σ = 20656710. Its totient is φ = 20656708.

The previous prime is 20656679. The next prime is 20656733. The reversal of 20656709 is 90765602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14668900 + 5987809 = 3830^2 + 2447^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20656709 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20656799) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10328354 + 10328355.

It is an arithmetic number, because the mean of its divisors is an integer number (10328355).

Almost surely, 2^20656709 is an apocalyptic number.

It is an amenable number.

20656709 is a deficient number, since it is larger than the sum of its proper divisors (1).

20656709 is an equidigital number, since it uses as much as digits as its factorization.

20656709 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 22680, while the sum is 35.

The square root of 20656709 is about 4544.9652363907. The cubic root of 20656709 is about 274.3807952415.

The spelling of 20656709 in words is "twenty million, six hundred fifty-six thousand, seven hundred nine".