18106662721 has 27 divisors (see below), whose sum is σ = 21573279459. Its totient is φ = 15152645088.

The previous prime is 18106662703. The next prime is 18106662733. The reversal of 18106662721 is 12726660181.

The square root of 18106662721 is 134561.

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

It can be written as a sum of positive squares in only one way, i.e., 16547992321 + 1558670400 = 128639^2 + 39480^2 .

It is not a de Polignac number, because 18106662721 - 2¹³ = 18106654529 is a prime.

It is a super-2 number, since 2×18106662721² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18106662701) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 44270365 + ... + 44270773.

Almost surely, 2^18106662721 is an apocalyptic number.

18106662721 is the 134561-st square number.

18106662721 is the 67281-st centered octagonal number.

It is an amenable number.

18106662721 is a deficient number, since it is larger than the sum of its proper divisors (3466616738).

18106662721 is an frugal number, since it uses more digits than its factorization.

18106662721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 926 (or 463 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 40.

The spelling of 18106662721 in words is "eighteen billion, one hundred six million, six hundred sixty-two thousand, seven hundred twenty-one".