18272781 has 6 divisors (see below), whose sum is σ = 26394030. Its totient is φ = 12181848.

The previous prime is 18272767. The next prime is 18272791. The reversal of 18272781 is 18727281.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 15139881 + 3132900 = 3891^2 + 1770^2 .

It is not a de Polignac number, because 18272781 - 2⁹ = 18272269 is a prime.

It is a super-2 number, since 2×18272781² = 667789050947922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18272701) 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 5 ways as a sum of consecutive naturals, for example, 1015146 + ... + 1015163.

It is an arithmetic number, because the mean of its divisors is an integer number (4399005).

Almost surely, 2^18272781 is an apocalyptic number.

It is an amenable number.

18272781 is a deficient number, since it is larger than the sum of its proper divisors (8121249).

18272781 is a wasteful number, since it uses less digits than its factorization.

18272781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2030315 (or 2030312 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 18272781 is about 4274.6673554793. The cubic root of 18272781 is about 263.3913751602.

The spelling of 18272781 in words is "eighteen million, two hundred seventy-two thousand, seven hundred eighty-one".