1323721666 has 4 divisors (see below), whose sum is σ = 1985582502. Its totient is φ = 661860832.

The previous prime is 1323721649. The next prime is 1323721667. The reversal of 1323721666 is 6661273231.

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

It can be written as a sum of positive squares in only one way, i.e., 1253514025 + 70207641 = 35405^2 + 8379^2 .

It is not an unprimeable number, because it can be changed into a prime (1323721667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330930415 + ... + 330930418.

Almost surely, 2^1323721666 is an apocalyptic number.

1323721666 is a deficient number, since it is larger than the sum of its proper divisors (661860836).

1323721666 is an equidigital number, since it uses as much as digits as its factorization.

1323721666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 661860835.

The product of its digits is 54432, while the sum is 37.

The square root of 1323721666 is about 36382.9859412336. The cubic root of 1323721666 is about 1097.9912834147.

Adding to 1323721666 its reverse (6661273231), we get a palindrome (7984994897).

The spelling of 1323721666 in words is "one billion, three hundred twenty-three million, seven hundred twenty-one thousand, six hundred sixty-six".