20709569 has 2 divisors, whose sum is σ = 20709570. Its totient is φ = 20709568.

The previous prime is 20709547. The next prime is 20709571. The reversal of 20709569 is 96590702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20611600 + 97969 = 4540^2 + 313^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20709569 is a prime.

It is a super-2 number, since 2×20709569² = 857772496331522, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 20709571, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20709539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10354784 + 10354785.

It is an arithmetic number, because the mean of its divisors is an integer number (10354785).

Almost surely, 2^20709569 is an apocalyptic number.

It is an amenable number.

20709569 is a deficient number, since it is larger than the sum of its proper divisors (1).

20709569 is an equidigital number, since it uses as much as digits as its factorization.

20709569 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34020, while the sum is 38.

The square root of 20709569 is about 4550.7767468862. The cubic root of 20709569 is about 274.6146404102.

The spelling of 20709569 in words is "twenty million, seven hundred nine thousand, five hundred sixty-nine".