1216317985 has 4 divisors (see below), whose sum is σ = 1459581588. Its totient is φ = 973054384.

The previous prime is 1216317967. The next prime is 1216317997. The reversal of 1216317985 is 5897136121.

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

It can be written as a sum of positive squares in 2 ways, for example, as 391881616 + 824436369 = 19796^2 + 28713^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216317985 - 2¹¹ = 1216315937 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 121631794 + ... + 121631803.

It is an arithmetic number, because the mean of its divisors is an integer number (364895397).

Almost surely, 2^1216317985 is an apocalyptic number.

It is an amenable number.

1216317985 is a deficient number, since it is larger than the sum of its proper divisors (243263603).

1216317985 is an equidigital number, since it uses as much as digits as its factorization.

1216317985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243263602.

The product of its digits is 90720, while the sum is 43.

The square root of 1216317985 is about 34875.7506729246. The cubic root of 1216317985 is about 1067.4536899435.

The spelling of 1216317985 in words is "one billion, two hundred sixteen million, three hundred seventeen thousand, nine hundred eighty-five".