1216236665 has 16 divisors (see below), whose sum is σ = 1740503808. Its totient is φ = 797729856.

The previous prime is 1216236653. The next prime is 1216236689. The reversal of 1216236665 is 5666326121.

It is a happy number.

It is not a de Polignac number, because 1216236665 - 2⁴ = 1216236649 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 754622 + ... + 756231.

It is an arithmetic number, because the mean of its divisors is an integer number (108781488).

Almost surely, 2^1216236665 is an apocalyptic number.

It is an amenable number.

1216236665 is a deficient number, since it is larger than the sum of its proper divisors (524267143).

1216236665 is a wasteful number, since it uses less digits than its factorization.

1216236665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1510888.

The product of its digits is 77760, while the sum is 38.

The square root of 1216236665 is about 34874.5848003958. The cubic root of 1216236665 is about 1067.4299003123.

The spelling of 1216236665 in words is "one billion, two hundred sixteen million, two hundred thirty-six thousand, six hundred sixty-five".