664123221 has 6 divisors (see below), whose sum is σ = 959289110. Its totient is φ = 442748808.

The previous prime is 664123219. The next prime is 664123237. The reversal of 664123221 is 122321466.

It can be written as a sum of positive squares in only one way, i.e., 488852100 + 175271121 = 22110^2 + 13239^2 .

It is not a de Polignac number, because 664123221 - 2¹ = 664123219 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 (664123021) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36895726 + ... + 36895743.

Almost surely, 2^664123221 is an apocalyptic number.

It is an amenable number.

664123221 is a deficient number, since it is larger than the sum of its proper divisors (295165889).

664123221 is a wasteful number, since it uses less digits than its factorization.

664123221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73791475 (or 73791472 counting only the distinct ones).

The product of its digits is 3456, while the sum is 27.

The square root of 664123221 is about 25770.5882936343. The cubic root of 664123221 is about 872.4680966871.

Adding to 664123221 its reverse (122321466), we get a palindrome (786444687).

The spelling of 664123221 in words is "six hundred sixty-four million, one hundred twenty-three thousand, two hundred twenty-one".