209764021 has 2 divisors, whose sum is σ = 209764022. Its totient is φ = 209764020.

The previous prime is 209764001. The next prime is 209764043. The reversal of 209764021 is 120467902.

209764021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 189612900 + 20151121 = 13770^2 + 4489^2 .

It is a cyclic number.

It is not a de Polignac number, because 209764021 - 2⁹ = 209763509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (209764001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104882010 + 104882011.

It is an arithmetic number, because the mean of its divisors is an integer number (104882011).

Almost surely, 2^209764021 is an apocalyptic number.

It is an amenable number.

209764021 is a deficient number, since it is larger than the sum of its proper divisors (1).

209764021 is an equidigital number, since it uses as much as digits as its factorization.

209764021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6048, while the sum is 31.

The square root of 209764021 is about 14483.2324085475. The cubic root of 209764021 is about 594.1694704392.

The spelling of 209764021 in words is "two hundred nine million, seven hundred sixty-four thousand, twenty-one".