21181697 has 2 divisors, whose sum is σ = 21181698. Its totient is φ = 21181696.

The previous prime is 21181679. The next prime is 21181703. The reversal of 21181697 is 79618112.

Together with previous prime (21181679) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14622976 + 6558721 = 3824^2 + 2561^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21181697 is a prime.

It is not a weakly prime, because it can be changed into another prime (21181627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10590848 + 10590849.

It is an arithmetic number, because the mean of its divisors is an integer number (10590849).

Almost surely, 2^21181697 is an apocalyptic number.

It is an amenable number.

21181697 is a deficient number, since it is larger than the sum of its proper divisors (1).

21181697 is an equidigital number, since it uses as much as digits as its factorization.

21181697 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6048, while the sum is 35.

The square root of 21181697 is about 4602.3577653199. The cubic root of 21181697 is about 276.6858293851.

The spelling of 21181697 in words is "twenty-one million, one hundred eighty-one thousand, six hundred ninety-seven".