20868509 has 2 divisors, whose sum is σ = 20868510. Its totient is φ = 20868508.

The previous prime is 20868499. The next prime is 20868539. The reversal of 20868509 is 90586802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13322500 + 7546009 = 3650^2 + 2747^2 .

It is a cyclic number.

It is not a de Polignac number, because 20868509 - 2²⁴ = 4091293 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 (20868539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10434254 + 10434255.

It is an arithmetic number, because the mean of its divisors is an integer number (10434255).

Almost surely, 2^20868509 is an apocalyptic number.

It is an amenable number.

20868509 is a deficient number, since it is larger than the sum of its proper divisors (1).

20868509 is an equidigital number, since it uses as much as digits as its factorization.

20868509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34560, while the sum is 38.

The square root of 20868509 is about 4568.2063219605. The cubic root of 20868509 is about 275.3153803205.

The spelling of 20868509 in words is "twenty million, eight hundred sixty-eight thousand, five hundred nine".