1221378666 has 16 divisors (see below), whose sum is σ = 2443345344. Its totient is φ = 407028224.

The previous prime is 1221378659. The next prime is 1221378667. The reversal of 1221378666 is 6668731221.

It is not an unprimeable number, because it can be changed into a prime (1221378667) 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 7 ways as a sum of consecutive naturals, for example, 5290 + ... + 49706.

It is an arithmetic number, because the mean of its divisors is an integer number (152709084).

Almost surely, 2^1221378666 is an apocalyptic number.

1221378666 is an abundant number, since it is smaller than the sum of its proper divisors (1221966678).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1221378666 is a wasteful number, since it uses less digits than its factorization.

1221378666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49005.

The product of its digits is 145152, while the sum is 42.

The square root of 1221378666 is about 34948.2283671147. The cubic root of 1221378666 is about 1068.9320774291.

The spelling of 1221378666 in words is "one billion, two hundred twenty-one million, three hundred seventy-eight thousand, six hundred sixty-six".