1321606666 has 4 divisors (see below), whose sum is σ = 1982410002. Its totient is φ = 660803332.

The previous prime is 1321606651. The next prime is 1321606697. The reversal of 1321606666 is 6666061231.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 6666061231 = 277 ⋅24065203.

It can be written as a sum of positive squares in only one way, i.e., 1230957225 + 90649441 = 35085^2 + 9521^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330401665 + ... + 330401668.

Almost surely, 2^1321606666 is an apocalyptic number.

1321606666 is a deficient number, since it is larger than the sum of its proper divisors (660803336).

1321606666 is an equidigital number, since it uses as much as digits as its factorization.

1321606666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 660803335.

The product of its (nonzero) digits is 46656, while the sum is 37.

The square root of 1321606666 is about 36353.9085381476. The cubic root of 1321606666 is about 1097.4061932785.

Adding to 1321606666 its reverse (6666061231), we get a palindrome (7987667897).

The spelling of 1321606666 in words is "one billion, three hundred twenty-one million, six hundred six thousand, six hundred sixty-six".