20681009 has 2 divisors, whose sum is σ = 20681010. Its totient is φ = 20681008.

The previous prime is 20680997. The next prime is 20681021. The reversal of 20681009 is 90018602.

It is a balanced prime because it is at equal distance from previous prime (20680997) and next prime (20681021).

It can be written as a sum of positive squares in only one way, i.e., 12271009 + 8410000 = 3503^2 + 2900^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20681009 is a prime.

It is not a weakly prime, because it can be changed into another prime (20681029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10340504 + 10340505.

It is an arithmetic number, because the mean of its divisors is an integer number (10340505).

Almost surely, 2^20681009 is an apocalyptic number.

It is an amenable number.

20681009 is a deficient number, since it is larger than the sum of its proper divisors (1).

20681009 is an equidigital number, since it uses as much as digits as its factorization.

20681009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 20681009 is about 4547.6377384308. The cubic root of 20681009 is about 274.4883444896.

The spelling of 20681009 in words is "twenty million, six hundred eighty-one thousand, nine".