21144046681 has 8 divisors (see below), whose sum is σ = 21545736264. Its totient is φ = 20742458880.

The previous prime is 21144046673. The next prime is 21144046687. The reversal of 21144046681 is 18664044112.

It can be written as a sum of positive squares in 4 ways, for example, as 2219917456 + 18924129225 = 47116^2 + 137565^2 .

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 21144046681 - 2³ = 21144046673 is a prime.

It is a super-2 number, since 2×21144046681² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21144046681.

It is not an unprimeable number, because it can be changed into a prime (21144046687) 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, 493371 + ... + 534511.

It is an arithmetic number, because the mean of its divisors is an integer number (2693217033).

Almost surely, 2^21144046681 is an apocalyptic number.

It is an amenable number.

21144046681 is a deficient number, since it is larger than the sum of its proper divisors (401689583).

21144046681 is an equidigital number, since it uses as much as digits as its factorization.

21144046681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50891.

The product of its (nonzero) digits is 36864, while the sum is 37.

It can be divided in two parts, 211440 and 46681, that added together give a triangular number (258121 = T₇₁₈).

The spelling of 21144046681 in words is "twenty-one billion, one hundred forty-four million, forty-six thousand, six hundred eighty-one".