18443781 has 20 divisors (see below), whose sum is σ = 27817900. Its totient is φ = 12177216.

The previous prime is 18443773. The next prime is 18443801. The reversal of 18443781 is 18734481.

It can be written as a sum of positive squares in 2 ways, for example, as 14699556 + 3744225 = 3834^2 + 1935^2 .

It is not a de Polignac number, because 18443781 - 2³ = 18443773 is a prime.

It is a super-2 number, since 2×18443781² = 680346115151922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18443081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 7785 + ... + 9873.

It is an arithmetic number, because the mean of its divisors is an integer number (1390895).

Almost surely, 2^18443781 is an apocalyptic number.

It is an amenable number.

18443781 is a deficient number, since it is larger than the sum of its proper divisors (9374119).

18443781 is a wasteful number, since it uses less digits than its factorization.

18443781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2210 (or 2201 counting only the distinct ones).

The product of its digits is 21504, while the sum is 36.

The square root of 18443781 is about 4294.6223349673. The cubic root of 18443781 is about 264.2104468677.

It can be divided in two parts, 1844 and 3781, that added together give a square (5625 = 75²).

The spelling of 18443781 in words is "eighteen million, four hundred forty-three thousand, seven hundred eighty-one".