661216845 has 16 divisors (see below), whose sum is σ = 1072441152. Its totient is φ = 347817600.

The previous prime is 661216793. The next prime is 661216859. The reversal of 661216845 is 548612166.

It is a happy number.

It is not a de Polignac number, because 661216845 - 2¹⁷ = 661085773 is a prime.

It is a super-2 number, since 2×661216845² = 874415432223508050, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 300831 + ... + 303020.

It is an arithmetic number, because the mean of its divisors is an integer number (67027572).

Almost surely, 2^661216845 is an apocalyptic number.

It is an amenable number.

661216845 is a deficient number, since it is larger than the sum of its proper divisors (411224307).

661216845 is a wasteful number, since it uses less digits than its factorization.

661216845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 603932.

The product of its digits is 69120, while the sum is 39.

The square root of 661216845 is about 25714.1370650465. The cubic root of 661216845 is about 871.1935197879.

The spelling of 661216845 in words is "six hundred sixty-one million, two hundred sixteen thousand, eight hundred forty-five".