21181975481 has 2 divisors, whose sum is σ = 21181975482. Its totient is φ = 21181975480.

The previous prime is 21181975453. The next prime is 21181975513. The reversal of 21181975481 is 18457918112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20935485481 + 246490000 = 144691^2 + 15700^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21181975481 is a prime.

It is a super-2 number, since 2×21181975481² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21181975411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10590987740 + 10590987741.

It is an arithmetic number, because the mean of its divisors is an integer number (10590987741).

Almost surely, 2^21181975481 is an apocalyptic number.

It is an amenable number.

21181975481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21181975481 is an equidigital number, since it uses as much as digits as its factorization.

21181975481 is an evil number, because the sum of its binary digits is even.

The product of its digits is 161280, while the sum is 47.

The spelling of 21181975481 in words is "twenty-one billion, one hundred eighty-one million, nine hundred seventy-five thousand, four hundred eighty-one".