18021720025 has 9 divisors (see below), whose sum is σ = 22347765181. Its totient is φ = 14416839040.

The previous prime is 18021720007. The next prime is 18021720049. The reversal of 18021720025 is 52002712081.

The square root of 18021720025 is 134245.

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

It can be written as a sum of positive squares in 4 ways, for example, as 2437693129 + 15584026896 = 49373^2 + 124836^2 .

It is not a de Polignac number, because 18021720025 - 2¹⁷ = 18021588953 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 18021719975 and 18021720002.

It is an unprimeable number.

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 in 8 ways as a sum of consecutive naturals, for example, 657801 + ... + 684649.

Almost surely, 2^18021720025 is an apocalyptic number.

18021720025 is the 134245-th square number.

18021720025 is the 67123-rd centered octagonal number.

It is an amenable number.

18021720025 is a deficient number, since it is larger than the sum of its proper divisors (4326045156).

18021720025 is an frugal number, since it uses more digits than its factorization.

18021720025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53708 (or 26854 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 28.

The spelling of 18021720025 in words is "eighteen billion, twenty-one million, seven hundred twenty thousand, twenty-five".