201661665 has 16 divisors (see below), whose sum is σ = 333067776. Its totient is φ = 104083200.

The previous prime is 201661651. The next prime is 201661673. The reversal of 201661665 is 566166102.

It is not a de Polignac number, because 201661665 - 2⁶ = 201661601 is a prime.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 216376 + ... + 217305.

It is an arithmetic number, because the mean of its divisors is an integer number (20816736).

Almost surely, 2^201661665 is an apocalyptic number.

It is an amenable number.

201661665 is a deficient number, since it is larger than the sum of its proper divisors (131406111).

201661665 is a wasteful number, since it uses less digits than its factorization.

201661665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 433720.

The product of its (nonzero) digits is 12960, while the sum is 33.

The square root of 201661665 is about 14200.7628316228. The cubic root of 201661665 is about 586.4186622129.

The spelling of 201661665 in words is "two hundred one million, six hundred sixty-one thousand, six hundred sixty-five".