21605179681 has 8 divisors (see below), whose sum is σ = 21760885440. Its totient is φ = 21450005328.

The previous prime is 21605179639. The next prime is 21605179693. The reversal of 21605179681 is 18697150612.

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 21605179681 - 2⁷ = 21605179553 is a prime.

It is a super-2 number, since 2×21605179681² (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 (21605179621) 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, 51066 + ... + 214051.

It is an arithmetic number, because the mean of its divisors is an integer number (2720110680).

Almost surely, 2^21605179681 is an apocalyptic number.

It is an amenable number.

21605179681 is a deficient number, since it is larger than the sum of its proper divisors (155705759).

21605179681 is a wasteful number, since it uses less digits than its factorization.

21605179681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265703.

The product of its (nonzero) digits is 181440, while the sum is 46.

The spelling of 21605179681 in words is "twenty-one billion, six hundred five million, one hundred seventy-nine thousand, six hundred eighty-one".