20528309 has 2 divisors, whose sum is σ = 20528310. Its totient is φ = 20528308.

The previous prime is 20528281. The next prime is 20528311. The reversal of 20528309 is 90382502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19140625 + 1387684 = 4375^2 + 1178^2 .

It is a cyclic number.

It is not a de Polignac number, because 20528309 - 2¹² = 20524213 is a prime.

It is a super-2 number, since 2×20528309² = 842822940798962, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 20528311, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20528369) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10264154 + 10264155.

It is an arithmetic number, because the mean of its divisors is an integer number (10264155).

Almost surely, 2^20528309 is an apocalyptic number.

It is an amenable number.

20528309 is a deficient number, since it is larger than the sum of its proper divisors (1).

20528309 is an equidigital number, since it uses as much as digits as its factorization.

20528309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 20528309 is about 4530.8176966195. The cubic root of 20528309 is about 273.8111055324.

The spelling of 20528309 in words is "twenty million, five hundred twenty-eight thousand, three hundred nine".