20817109 has 2 divisors, whose sum is σ = 20817110. Its totient is φ = 20817108.

The previous prime is 20817107. The next prime is 20817127. The reversal of 20817109 is 90171802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18576100 + 2241009 = 4310^2 + 1497^2 .

It is a cyclic number.

It is not a de Polignac number, because 20817109 - 2¹ = 20817107 is a prime.

Together with 20817107, 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 (20817107) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10408554 + 10408555.

It is an arithmetic number, because the mean of its divisors is an integer number (10408555).

Almost surely, 2^20817109 is an apocalyptic number.

It is an amenable number.

20817109 is a deficient number, since it is larger than the sum of its proper divisors (1).

20817109 is an equidigital number, since it uses as much as digits as its factorization.

20817109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 20817109 is about 4562.5770130487. The cubic root of 20817109 is about 275.0891567666.

The spelling of 20817109 in words is "twenty million, eight hundred seventeen thousand, one hundred nine".