18639621729 has 27 divisors (see below), whose sum is σ = 28611506937. Its totient is φ = 11691080064.

The previous prime is 18639621719. The next prime is 18639621739. The reversal of 18639621729 is 92712693681.

The square root of 18639621729 is 136527.

It is a perfect power (a square), and thus also a powerful number.

18639621729 is a `hidden beast` number, since 1 + 8 + 6 + 3 + 9 + 621 + 7 + 2 + 9 = 666.

It is an interprime number because it is at equal distance from previous prime (18639621719) and next prime (18639621739).

It can be written as a sum of positive squares in 4 ways, for example, as 2230011729 + 16409610000 = 47223^2 + 128100^2 .

It is not a de Polignac number, because 18639621729 - 2⁵ = 18639621697 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18639621719) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 6961539 + ... + 6964215.

Almost surely, 2^18639621729 is an apocalyptic number.

18639621729 is the 136527-th square number.

18639621729 is the 68264-th centered octagonal number.

It is an amenable number.

18639621729 is a deficient number, since it is larger than the sum of its proper divisors (9971885208).

18639621729 is an frugal number, since it uses more digits than its factorization.

18639621729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5394 (or 2697 counting only the distinct ones).

The product of its digits is 1959552, while the sum is 54.

The spelling of 18639621729 in words is "eighteen billion, six hundred thirty-nine million, six hundred twenty-one thousand, seven hundred twenty-nine".