1021640209 has 2 divisors, whose sum is σ = 1021640210. Its totient is φ = 1021640208.

The previous prime is 1021640171. The next prime is 1021640231. The reversal of 1021640209 is 9020461201.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 907214400 + 114425809 = 30120^2 + 10697^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1021640209 is a prime.

It is not a weakly prime, because it can be changed into another prime (1021640299) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 510820104 + 510820105.

It is an arithmetic number, because the mean of its divisors is an integer number (510820105).

Almost surely, 2^1021640209 is an apocalyptic number.

It is an amenable number.

1021640209 is a deficient number, since it is larger than the sum of its proper divisors (1).

1021640209 is an equidigital number, since it uses as much as digits as its factorization.

1021640209 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 25.

The square root of 1021640209 is about 31963.1069985382. The cubic root of 1021640209 is about 1007.1619864937.

The spelling of 1021640209 in words is "one billion, twenty-one million, six hundred forty thousand, two hundred nine".