21453181613 has 2 divisors, whose sum is σ = 21453181614. Its totient is φ = 21453181612.

The previous prime is 21453181609. The next prime is 21453181669. The reversal of 21453181613 is 31618135412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13418210569 + 8034971044 = 115837^2 + 89638^2 .

It is a cyclic number.

It is not a de Polignac number, because 21453181613 - 2² = 21453181609 is a prime.

It is a super-2 number, since 2×21453181613² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21453180613) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10726590806 + 10726590807.

It is an arithmetic number, because the mean of its divisors is an integer number (10726590807).

Almost surely, 2^21453181613 is an apocalyptic number.

It is an amenable number.

21453181613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21453181613 is an equidigital number, since it uses as much as digits as its factorization.

21453181613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17280, while the sum is 35.

The spelling of 21453181613 in words is "twenty-one billion, four hundred fifty-three million, one hundred eighty-one thousand, six hundred thirteen".