21667357218 has 64 divisors (see below), whose sum is σ = 49419095040. Its totient is φ = 6278098752.

The previous prime is 21667357193. The next prime is 21667357219. The reversal of 21667357218 is 81275376612.

It is not an unprimeable number, because it can be changed into a prime (21667357219) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 203721 + ... + 291267.

It is an arithmetic number, because the mean of its divisors is an integer number (772173360).

Almost surely, 2^21667357218 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21667357218, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24709547520).

21667357218 is an abundant number, since it is smaller than the sum of its proper divisors (27751737822).

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

21667357218 is a wasteful number, since it uses less digits than its factorization.

21667357218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87751.

The product of its digits is 846720, while the sum is 48.

It can be divided in two parts, 21667 and 357218, that added together give a triangular number (378885 = T₈₇₀).

The spelling of 21667357218 in words is "twenty-one billion, six hundred sixty-seven million, three hundred fifty-seven thousand, two hundred eighteen".