21655828081 has 8 divisors (see below), whose sum is σ = 21814073064. Its totient is φ = 21497963520.

The previous prime is 21655828057. The next prime is 21655828091. The reversal of 21655828081 is 18082855612.

It can be written as a sum of positive squares in 4 ways, for example, as 3838917681 + 17816910400 = 61959^2 + 133480^2 .

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 21655828081 - 2⁵ = 21655828049 is a prime.

It is a super-2 number, since 2×21655828081² (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 (21655828091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19665 + ... + 209041.

It is an arithmetic number, because the mean of its divisors is an integer number (2726759133).

Almost surely, 2^21655828081 is an apocalyptic number.

It is an amenable number.

21655828081 is a deficient number, since it is larger than the sum of its proper divisors (158244983).

21655828081 is a wasteful number, since it uses less digits than its factorization.

21655828081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 190211.

The product of its (nonzero) digits is 307200, while the sum is 46.

The spelling of 21655828081 in words is "twenty-one billion, six hundred fifty-five million, eight hundred twenty-eight thousand, eighty-one".