20644653209 has 2 divisors, whose sum is σ = 20644653210. Its totient is φ = 20644653208.

The previous prime is 20644653199. The next prime is 20644653343. The reversal of 20644653209 is 90235644602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20603731600 + 40921609 = 143540^2 + 6397^2 .

It is a cyclic number.

It is not a de Polignac number, because 20644653209 - 2²⁴ = 20627875993 is a prime.

It is a super-2 number, since 2×20644653209² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20644653709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10322326604 + 10322326605.

It is an arithmetic number, because the mean of its divisors is an integer number (10322326605).

Almost surely, 2^20644653209 is an apocalyptic number.

It is an amenable number.

20644653209 is a deficient number, since it is larger than the sum of its proper divisors (1).

20644653209 is an equidigital number, since it uses as much as digits as its factorization.

20644653209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 311040, while the sum is 41.

The spelling of 20644653209 in words is "twenty billion, six hundred forty-four million, six hundred fifty-three thousand, two hundred nine".