816121618 has 48 divisors (see below), whose sum is σ = 1413402696. Its totient is φ = 352035840.

The previous prime is 816121609. The next prime is 816121619.

It is a happy number.

816121618 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in 12 ways, for example, as 58936329 + 757185289 = 7677^2 + 27517^2 .

It is a Harshad number since it is a multiple of its sum of digits (34).

It is an alternating number because its digits alternate between even and odd.

It is not an unprimeable number, because it can be changed into a prime (816121619) 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 23 ways as a sum of consecutive naturals, for example, 993648 + ... + 994468.

Almost surely, 2^816121618 is an apocalyptic number.

816121618 is a deficient number, since it is larger than the sum of its proper divisors (597281078).

816121618 is a wasteful number, since it uses less digits than its factorization.

816121618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1039 (or 1026 counting only the distinct ones).

The product of its digits is 4608, while the sum is 34.

The square root of 816121618 is about 28567.8423756503. The cubic root of 816121618 is about 934.5121681422.

The spelling of 816121618 in words is "eight hundred sixteen million, one hundred twenty-one thousand, six hundred eighteen".