221665641 has 4 divisors (see below), whose sum is σ = 295554192. Its totient is φ = 147777092.

The previous prime is 221665637. The next prime is 221665657. The reversal of 221665641 is 146566122.

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 a cyclic number.

It is not a de Polignac number, because 221665641 - 2² = 221665637 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (221665141) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36944271 + ... + 36944276.

It is an arithmetic number, because the mean of its divisors is an integer number (73888548).

Almost surely, 2^221665641 is an apocalyptic number.

It is an amenable number.

221665641 is a deficient number, since it is larger than the sum of its proper divisors (73888551).

221665641 is an equidigital number, since it uses as much as digits as its factorization.

221665641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73888550.

The product of its digits is 17280, while the sum is 33.

The square root of 221665641 is about 14888.4398443893. The cubic root of 221665641 is about 605.2007539044.

The spelling of 221665641 in words is "two hundred twenty-one million, six hundred sixty-five thousand, six hundred forty-one".