20101009 has 2 divisors, whose sum is σ = 20101010. Its totient is φ = 20101008.

The previous prime is 20101001. The next prime is 20101013. The reversal of 20101009 is 90010102.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17766225 + 2334784 = 4215^2 + 1528^2 .

It is a cyclic number.

It is not a de Polignac number, because 20101009 - 2³ = 20101001 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20101009.

It is not a weakly prime, because it can be changed into another prime (20101001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10050504 + 10050505.

It is an arithmetic number, because the mean of its divisors is an integer number (10050505).

Almost surely, 2^20101009 is an apocalyptic number.

It is an amenable number.

20101009 is a deficient number, since it is larger than the sum of its proper divisors (1).

20101009 is an equidigital number, since it uses as much as digits as its factorization.

20101009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18, while the sum is 13.

The square root of 20101009 is about 4483.4148815384. The cubic root of 20101009 is about 271.8979621950.

The spelling of 20101009 in words is "twenty million, one hundred one thousand, nine".