20736509 has 2 divisors, whose sum is σ = 20736510. Its totient is φ = 20736508.

The previous prime is 20736491. The next prime is 20736511. The reversal of 20736509 is 90563702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11868025 + 8868484 = 3445^2 + 2978^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20736509 is a prime.

Together with 20736511, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20736589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10368254 + 10368255.

It is an arithmetic number, because the mean of its divisors is an integer number (10368255).

Almost surely, 2^20736509 is an apocalyptic number.

It is an amenable number.

20736509 is a deficient number, since it is larger than the sum of its proper divisors (1).

20736509 is an equidigital number, since it uses as much as digits as its factorization.

20736509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11340, while the sum is 32.

The square root of 20736509 is about 4553.7357191651. The cubic root of 20736509 is about 274.7336661093.

The spelling of 20736509 in words is "twenty million, seven hundred thirty-six thousand, five hundred nine".