20021009809 has 2 divisors, whose sum is σ = 20021009810. Its totient is φ = 20021009808.

The previous prime is 20021009777. The next prime is 20021009849. The reversal of 20021009809 is 90890012002.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19695315600 + 325694209 = 140340^2 + 18047^2 .

It is a cyclic number.

It is not a de Polignac number, because 20021009809 - 2⁵ = 20021009777 is a prime.

It is not a weakly prime, because it can be changed into another prime (20021009849) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10010504904 + 10010504905.

It is an arithmetic number, because the mean of its divisors is an integer number (10010504905).

Almost surely, 2^20021009809 is an apocalyptic number.

It is an amenable number.

20021009809 is a deficient number, since it is larger than the sum of its proper divisors (1).

20021009809 is an equidigital number, since it uses as much as digits as its factorization.

20021009809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2592, while the sum is 31.

The spelling of 20021009809 in words is "twenty billion, twenty-one million, nine thousand, eight hundred nine".