221488661 has 4 divisors (see below), whose sum is σ = 221805324. Its totient is φ = 221172000.

The previous prime is 221488639. The next prime is 221488679. The reversal of 221488661 is 166884122.

It is a happy number.

221488661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 90820900 + 130667761 = 9530^2 + 11431^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221488661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221488061) 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, 157280 + ... + 158681.

It is an arithmetic number, because the mean of its divisors is an integer number (55451331).

Almost surely, 2^221488661 is an apocalyptic number.

It is an amenable number.

221488661 is a deficient number, since it is larger than the sum of its proper divisors (316663).

221488661 is an equidigital number, since it uses as much as digits as its factorization.

221488661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 316662.

The product of its digits is 36864, while the sum is 38.

The square root of 221488661 is about 14882.4951201067. The cubic root of 221488661 is about 605.0396449671.

The spelling of 221488661 in words is "two hundred twenty-one million, four hundred eighty-eight thousand, six hundred sixty-one".