2021121209 has 2 divisors, whose sum is σ = 2021121210. Its totient is φ = 2021121208.

The previous prime is 2021121191. The next prime is 2021121233. The reversal of 2021121209 is 9021211202.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1752259600 + 268861609 = 41860^2 + 16397^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2021121209 is a prime.

It is not a weakly prime, because it can be changed into another prime (2021121269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1010560604 + 1010560605.

It is an arithmetic number, because the mean of its divisors is an integer number (1010560605).

Almost surely, 2^2021121209 is an apocalyptic number.

It is an amenable number.

2021121209 is a deficient number, since it is larger than the sum of its proper divisors (1).

2021121209 is an equidigital number, since it uses as much as digits as its factorization.

2021121209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 2021121209 is about 44956.8816645461. The cubic root of 2021121209 is about 1264.3407041114.

The spelling of 2021121209 in words is "two billion, twenty-one million, one hundred twenty-one thousand, two hundred nine".