21208545181 has 8 divisors (see below), whose sum is σ = 21449597400. Its totient is φ = 20968338240.

The previous prime is 21208545139. The next prime is 21208545187. The reversal of 21208545181 is 18154580212.

It can be written as a sum of positive squares in 4 ways, for example, as 108368100 + 21100177081 = 10410^2 + 145259^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21208545181 is a prime.

It is a super-2 number, since 2×21208545181² (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 21208545181.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21208545187) 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, 160786 + ... + 261283.

It is an arithmetic number, because the mean of its divisors is an integer number (2681199675).

Almost surely, 2^21208545181 is an apocalyptic number.

It is an amenable number.

21208545181 is a deficient number, since it is larger than the sum of its proper divisors (241052219).

21208545181 is a wasteful number, since it uses less digits than its factorization.

21208545181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 422639.

The product of its (nonzero) digits is 25600, while the sum is 37.

The spelling of 21208545181 in words is "twenty-one billion, two hundred eight million, five hundred forty-five thousand, one hundred eighty-one".