20808779 has 2 divisors, whose sum is σ = 20808780. Its totient is φ = 20808778.

The previous prime is 20808761. The next prime is 20808787. The reversal of 20808779 is 97780802.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20808779 - 2²⁰ = 19760203 is a prime.

It is not a weakly prime, because it can be changed into another prime (20808079) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10404389 + 10404390.

It is an arithmetic number, because the mean of its divisors is an integer number (10404390).

Almost surely, 2^20808779 is an apocalyptic number.

20808779 is a deficient number, since it is larger than the sum of its proper divisors (1).

20808779 is an equidigital number, since it uses as much as digits as its factorization.

20808779 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 56448, while the sum is 41.

The square root of 20808779 is about 4561.6640604060. The cubic root of 20808779 is about 275.0524594136.

The spelling of 20808779 in words is "twenty million, eight hundred eight thousand, seven hundred seventy-nine".