1216441665 has 32 divisors (see below), whose sum is σ = 2167948800. Its totient is φ = 647153280.

The previous prime is 1216441661. The next prime is 1216441673. The reversal of 1216441665 is 5661446121.

1216441665 is a `hidden beast` number, since 1 + 2 + 1 + 644 + 1 + 6 + 6 + 5 = 666.

It is not a de Polignac number, because 1216441665 - 2² = 1216441661 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1216441661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 44200 + ... + 66230.

It is an arithmetic number, because the mean of its divisors is an integer number (67748400).

Almost surely, 2^1216441665 is an apocalyptic number.

1216441665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1216441665 is a deficient number, since it is larger than the sum of its proper divisors (951507135).

1216441665 is a wasteful number, since it uses less digits than its factorization.

1216441665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22454 (or 22448 counting only the distinct ones).

The product of its digits is 34560, while the sum is 36.

The square root of 1216441665 is about 34877.5237796493. The cubic root of 1216441665 is about 1067.4898696814.

Adding to 1216441665 its reverse (5661446121), we get a palindrome (6877887786).

The spelling of 1216441665 in words is "one billion, two hundred sixteen million, four hundred forty-one thousand, six hundred sixty-five".