201664821 has 4 divisors (see below), whose sum is σ = 268886432. Its totient is φ = 134443212.

The previous prime is 201664819. The next prime is 201664831. The reversal of 201664821 is 128466102.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 201664821 - 2¹ = 201664819 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (201664831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33610801 + ... + 33610806.

It is an arithmetic number, because the mean of its divisors is an integer number (67221608).

Almost surely, 2^201664821 is an apocalyptic number.

It is an amenable number.

201664821 is a deficient number, since it is larger than the sum of its proper divisors (67221611).

201664821 is an equidigital number, since it uses as much as digits as its factorization.

201664821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67221610.

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 201664821 is about 14200.8739519792. The cubic root of 201664821 is about 586.4217213428.

The spelling of 201664821 in words is "two hundred one million, six hundred sixty-four thousand, eight hundred twenty-one".