21881517181 has 12 divisors (see below), whose sum is σ = 23657068764. Its totient is φ = 20224238400.

The previous prime is 21881517179. The next prime is 21881517271. The reversal of 21881517181 is 18171518812.

It can be written as a sum of positive squares in 2 ways, for example, as 953265625 + 20928251556 = 30875^2 + 144666^2 .

It is not a de Polignac number, because 21881517181 - 2¹ = 21881517179 is a prime.

It is a super-2 number, since 2×21881517181² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21881517101) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 724390 + ... + 753991.

It is an arithmetic number, because the mean of its divisors is an integer number (1971422397).

Almost surely, 2^21881517181 is an apocalyptic number.

It is an amenable number.

21881517181 is a deficient number, since it is larger than the sum of its proper divisors (1775551583).

21881517181 is a wasteful number, since it uses less digits than its factorization.

21881517181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1478460 (or 1478441 counting only the distinct ones).

The product of its digits is 35840, while the sum is 43.

The spelling of 21881517181 in words is "twenty-one billion, eight hundred eighty-one million, five hundred seventeen thousand, one hundred eighty-one".