221710661 has 4 divisors (see below), whose sum is σ = 225345324. Its totient is φ = 218076000.

The previous prime is 221710603. The next prime is 221710711. The reversal of 221710661 is 166017122.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166017122 = 2 ⋅83008561.

It can be written as a sum of positive squares in 2 ways, for example, as 73017025 + 148693636 = 8545^2 + 12194^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221710661 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 221710661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221710061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1817240 + ... + 1817361.

It is an arithmetic number, because the mean of its divisors is an integer number (56336331).

Almost surely, 2^221710661 is an apocalyptic number.

It is an amenable number.

221710661 is a deficient number, since it is larger than the sum of its proper divisors (3634663).

221710661 is an equidigital number, since it uses as much as digits as its factorization.

221710661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3634662.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 221710661 is about 14889.9516789008. The cubic root of 221710661 is about 605.2417229565.

Adding to 221710661 its reverse (166017122), we get a palindrome (387727783).

The spelling of 221710661 in words is "two hundred twenty-one million, seven hundred ten thousand, six hundred sixty-one".