664142221 has 4 divisors (see below), whose sum is σ = 666409212. Its totient is φ = 661875232.

The previous prime is 664142201. The next prime is 664142251. The reversal of 664142221 is 122241466.

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 491508900 + 172633321 = 22170^2 + 13139^2 .

It is a cyclic number.

It is not a de Polignac number, because 664142221 - 2⁵ = 664142189 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 664142221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664142201) 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, 1133056 + ... + 1133641.

It is an arithmetic number, because the mean of its divisors is an integer number (166602303).

Almost surely, 2^664142221 is an apocalyptic number.

It is an amenable number.

664142221 is a deficient number, since it is larger than the sum of its proper divisors (2266991).

664142221 is a wasteful number, since it uses less digits than its factorization.

664142221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2266990.

The product of its digits is 4608, while the sum is 28.

The square root of 664142221 is about 25770.9569282943. The cubic root of 664142221 is about 872.4764167976.

Adding to 664142221 its reverse (122241466), we get a palindrome (786383687).

It can be divided in two parts, 66414 and 2221, that added together give a triangular number (68635 = T₃₇₀).

The spelling of 664142221 in words is "six hundred sixty-four million, one hundred forty-two thousand, two hundred twenty-one".