20636509 has 2 divisors, whose sum is σ = 20636510. Its totient is φ = 20636508.

The previous prime is 20636507. The next prime is 20636513. The reversal of 20636509 is 90563602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20115225 + 521284 = 4485^2 + 722^2 .

It is a cyclic number.

It is not a de Polignac number, because 20636509 - 2¹ = 20636507 is a prime.

Together with 20636507, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20636503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10318254 + 10318255.

It is an arithmetic number, because the mean of its divisors is an integer number (10318255).

Almost surely, 2^20636509 is an apocalyptic number.

It is an amenable number.

20636509 is a deficient number, since it is larger than the sum of its proper divisors (1).

20636509 is an equidigital number, since it uses as much as digits as its factorization.

20636509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9720, while the sum is 31.

The square root of 20636509 is about 4542.7424536286. The cubic root of 20636509 is about 274.2913279455.

The spelling of 20636509 in words is "twenty million, six hundred thirty-six thousand, five hundred nine".