18019840644 has 81 divisors (see below), whose sum is σ = 49352214639. Its totient is φ = 5541344640.

The previous prime is 18019840639. The next prime is 18019840681. The reversal of 18019840644 is 44604891081.

The square root of 18019840644 is 134238.

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

18019840644 is a `hidden beast` number, since 18 + 0 + 198 + 406 + 44 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 360620100 + 17659220544 = 18990^2 + 132888^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 18019840644.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 10469704 + ... + 10471424.

Almost surely, 2^18019840644 is an apocalyptic number.

18019840644 is the 134238-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18019840644

18019840644 is an abundant number, since it is smaller than the sum of its proper divisors (31332373995).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18019840644 is a wasteful number, since it uses less digits than its factorization.

18019840644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3478 (or 1739 counting only the distinct ones).

The product of its (nonzero) digits is 221184, while the sum is 45.

The spelling of 18019840644 in words is "eighteen billion, nineteen million, eight hundred forty thousand, six hundred forty-four".