20985481 has 32 divisors (see below), whose sum is σ = 25804800.
Its totient is φ = 16848000.
The previous prime is 20985479. The next prime is 20985487. The reversal of 20985481 is 18458902.
20985481 = T84 + T85 + ... +
20985481 is a nontrivial binomial coefficient, being equal to C(6479, 2).
It is a cyclic number.
It is not a de Polignac number, because 20985481 - 21 = 20985479 is a prime.
It is a super-2 number, since 2×209854812 = 880780825602722, which contains 22 as substring.
It is a Smith number, since the sum of its digits (37) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.
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 20985481.
It is not an unprimeable number, because it can be changed into a prime (20985487) by changing a digit.
It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 265600 + ... + 265678.
It is an arithmetic number, because the mean of its divisors is an integer number (806400).
Almost surely, 220985481 is an apocalyptic number.
20985481 is the 6478-th triangular number and also the 2449-th nonagonal number.
20985481 is the 2160-th centered nonagonal number.
It is an amenable number.
20985481 is a deficient number, since it is larger than the sum of its proper divisors (4819319).
20985481 is a wasteful number, since it uses less digits than its factorization.
20985481 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 181.
The product of its (nonzero) digits is 23040, while the sum is 37.
The square root of 20985481 is about 4580.9912682737.
The cubic root of 20985481 is about 275.8288207251.
The spelling of 20985481 in words is "twenty million, nine hundred eighty-five thousand, four hundred eighty-one".