221666365 has 8 divisors (see below), whose sum is σ = 266451768. Its totient is φ = 177031680.

The previous prime is 221666323. The next prime is 221666381. The reversal of 221666365 is 563666122.

It can be written as a sum of positive squares in 4 ways, for example, as 16088121 + 205578244 = 4011^2 + 14338^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 221666365 - 2¹⁵ = 221633597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34416 + ... + 40345.

It is an arithmetic number, because the mean of its divisors is an integer number (33306471).

Almost surely, 2^221666365 is an apocalyptic number.

It is an amenable number.

221666365 is a deficient number, since it is larger than the sum of its proper divisors (44785403).

221666365 is an equidigital number, since it uses as much as digits as its factorization.

221666365 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75359.

The product of its digits is 77760, while the sum is 37.

The square root of 221666365 is about 14888.4641585356. The cubic root of 221666365 is about 605.2014128020.

The spelling of 221666365 in words is "two hundred twenty-one million, six hundred sixty-six thousand, three hundred sixty-five".