20642009 has 2 divisors, whose sum is σ = 20642010. Its totient is φ = 20642008.

The previous prime is 20641993. The next prime is 20642023. The reversal of 20642009 is 90024602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15015625 + 5626384 = 3875^2 + 2372^2 .

It is a cyclic number.

It is not a de Polignac number, because 20642009 - 2⁴ = 20641993 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20642059) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10321004 + 10321005.

It is an arithmetic number, because the mean of its divisors is an integer number (10321005).

Almost surely, 2^20642009 is an apocalyptic number.

It is an amenable number.

20642009 is a deficient number, since it is larger than the sum of its proper divisors (1).

20642009 is an equidigital number, since it uses as much as digits as its factorization.

20642009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 20642009 is about 4543.3477744940. The cubic root of 20642009 is about 274.3156936348.

The spelling of 20642009 in words is "twenty million, six hundred forty-two thousand, nine".