221661604 has 6 divisors (see below), whose sum is σ = 387907814. Its totient is φ = 110830800.

The previous prime is 221661593. The next prime is 221661611. The reversal of 221661604 is 406166122.

It can be written as a sum of positive squares in only one way, i.e., 217621504 + 4040100 = 14752^2 + 2010^2 .

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 27707697 + ... + 27707704.

Almost surely, 2^221661604 is an apocalyptic number.

It is an amenable number.

221661604 is a deficient number, since it is larger than the sum of its proper divisors (166246210).

221661604 is a wasteful number, since it uses less digits than its factorization.

221661604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55415405 (or 55415403 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 221661604 is about 14888.3042687876. The cubic root of 221661604 is about 605.1970798870.

It can be divided in two parts, 221 and 661604, that added together give a triangular number (661825 = T₁₁₅₀).

The spelling of 221661604 in words is "two hundred twenty-one million, six hundred sixty-one thousand, six hundred four".