21797081867808 has 144 divisors (see below), whose sum is σ = 66964145930136. Its totient is φ = 6685636976640.

The previous prime is 21797081867783. The next prime is 21797081867833. The reversal of 21797081867808 is 80876818079712.

It is an interprime number because it is at equal distance from previous prime (21797081867783) and next prime (21797081867833).

It can be written as a sum of positive squares in 4 ways, for example, as 3855520748304 + 17941561119504 = 1963548^2 + 4235748^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-2 number, since 2×21797081867808² (a number of 27 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7995913 + ... + 10369608.

Almost surely, 2^{21797081867808} is an apocalyptic number.

It is an amenable number.

21797081867808 is an abundant number, since it is smaller than the sum of its proper divisors (45167064062328).

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

21797081867808 is a wasteful number, since it uses less digits than its factorization.

21797081867808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18365867 (or 18365856 counting only the distinct ones).

The product of its (nonzero) digits is 151732224, while the sum is 72.

The spelling of 21797081867808 in words is "twenty-one trillion, seven hundred ninety-seven billion, eighty-one million, eight hundred sixty-seven thousand, eight hundred eight".