221664325 has 6 divisors (see below), whose sum is σ = 274863794. Its totient is φ = 177331440.

The previous prime is 221664293. The next prime is 221664337. The reversal of 221664325 is 523466122.

It can be written as a sum of positive squares in 3 ways, for example, as 4072324 + 217592001 = 2018^2 + 14751^2 .

It is not a de Polignac number, because 221664325 - 2⁵ = 221664293 is a prime.

It is a Duffinian number.

It is a congruent number.

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 in 5 ways as a sum of consecutive naturals, for example, 4433262 + ... + 4433311.

Almost surely, 2^221664325 is an apocalyptic number.

221664325 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

221664325 is a deficient number, since it is larger than the sum of its proper divisors (53199469).

221664325 is an equidigital number, since it uses as much as digits as its factorization.

221664325 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8866583 (or 8866578 counting only the distinct ones).

The product of its digits is 17280, while the sum is 31.

The square root of 221664325 is about 14888.3956489610. The cubic root of 221664325 is about 605.1995562360.

The spelling of 221664325 in words is "two hundred twenty-one million, six hundred sixty-four thousand, three hundred twenty-five".