8161221618 has 48 divisors (see below), whose sum is σ = 19300278816. Its totient is φ = 2471800320.

The previous prime is 8161221617. The next prime is 8161221631.

8161221618 is a `hidden beast` number, since 8 + 1 + 6 + 12 + 21 + 618 = 666.

8161221618 is nontrivially palindromic in base 10.

It is a super-2 number, since 2×8161221618² (a number of 21 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (8161221617) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 408621 + ... + 428127.

It is an arithmetic number, because the mean of its divisors is an integer number (402089142).

Almost surely, 2^8161221618 is an apocalyptic number.

8161221618 is an abundant number, since it is smaller than the sum of its proper divisors (11139057198).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

8161221618 is a wasteful number, since it uses less digits than its factorization.

8161221618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21639 (or 21636 counting only the distinct ones).

The product of its digits is 9216, while the sum is 36.

The square root of 8161221618 is about 90339.4798413185. The cubic root of 8161221618 is about 2013.3458804814.

The spelling of 8161221618 in words is "eight billion, one hundred sixty-one million, two hundred twenty-one thousand, six hundred eighteen".