20402009 has 2 divisors, whose sum is σ = 20402010. Its totient is φ = 20402008.

The previous prime is 20401973. The next prime is 20402017. The reversal of 20402009 is 90020402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19998784 + 403225 = 4472^2 + 635^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20402009 is a prime.

It is not a weakly prime, because it can be changed into another prime (20402099) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10201004 + 10201005.

It is an arithmetic number, because the mean of its divisors is an integer number (10201005).

Almost surely, 2^20402009 is an apocalyptic number.

It is an amenable number.

20402009 is a deficient number, since it is larger than the sum of its proper divisors (1).

20402009 is an equidigital number, since it uses as much as digits as its factorization.

20402009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 17.

The square root of 20402009 is about 4516.8583108174. The cubic root of 20402009 is about 273.2484108908.

The spelling of 20402009 in words is "twenty million, four hundred two thousand, nine".