20506517 has 2 divisors, whose sum is σ = 20506518. Its totient is φ = 20506516.

The previous prime is 20506513. The next prime is 20506543. The reversal of 20506517 is 71560502.

It is an a-pointer prime, because the next prime (20506543) can be obtained adding 20506517 to its sum of digits (26).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20376196 + 130321 = 4514^2 + 361^2 .

It is a cyclic number.

It is not a de Polignac number, because 20506517 - 2² = 20506513 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20506513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10253258 + 10253259.

It is an arithmetic number, because the mean of its divisors is an integer number (10253259).

Almost surely, 2^20506517 is an apocalyptic number.

It is an amenable number.

20506517 is a deficient number, since it is larger than the sum of its proper divisors (1).

20506517 is an equidigital number, since it uses as much as digits as its factorization.

20506517 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2100, while the sum is 26.

The square root of 20506517 is about 4528.4121941360. The cubic root of 20506517 is about 273.7141823964.

The spelling of 20506517 in words is "twenty million, five hundred six thousand, five hundred seventeen".