21275471681 has 2 divisors, whose sum is σ = 21275471682. Its totient is φ = 21275471680.

The previous prime is 21275471599. The next prime is 21275471683. The reversal of 21275471681 is 18617457212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13943831056 + 7331640625 = 118084^2 + 85625^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21275471681 is a prime.

It is a super-2 number, since 2×21275471681² (a number of 21 digits) contains 22 as substring.

Together with 21275471683, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21275471683) 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 as a sum of consecutive naturals, namely, 10637735840 + 10637735841.

It is an arithmetic number, because the mean of its divisors is an integer number (10637735841).

Almost surely, 2^21275471681 is an apocalyptic number.

It is an amenable number.

21275471681 is a deficient number, since it is larger than the sum of its proper divisors (1).

21275471681 is an equidigital number, since it uses as much as digits as its factorization.

21275471681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 188160, while the sum is 44.

The spelling of 21275471681 in words is "twenty-one billion, two hundred seventy-five million, four hundred seventy-one thousand, six hundred eighty-one".