21218324681 has 8 divisors (see below), whose sum is σ = 21326705928. Its totient is φ = 21110112000.

The previous prime is 21218324663. The next prime is 21218324707. The reversal of 21218324681 is 18642381212.

It can be written as a sum of positive squares in 4 ways, for example, as 5135012281 + 16083312400 = 71659^2 + 126820^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21218324681 - 2¹⁴ = 21218308297 is a prime.

It is a super-2 number, since 2×21218324681² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21218354681) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 214211 + ... + 297191.

It is an arithmetic number, because the mean of its divisors is an integer number (2665838241).

Almost surely, 2^21218324681 is an apocalyptic number.

It is an amenable number.

21218324681 is a deficient number, since it is larger than the sum of its proper divisors (108381247).

21218324681 is a wasteful number, since it uses less digits than its factorization.

21218324681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84283.

The product of its digits is 36864, while the sum is 38.

The spelling of 21218324681 in words is "twenty-one billion, two hundred eighteen million, three hundred twenty-four thousand, six hundred eighty-one".