18271661 has 4 divisors (see below), whose sum is σ = 18281052. Its totient is φ = 18262272.

The previous prime is 18271657. The next prime is 18271663. The reversal of 18271661 is 16617281.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 16617281 = 1987 ⋅8363.

It can be written as a sum of positive squares in 2 ways, for example, as 7806436 + 10465225 = 2794^2 + 3235^2 .

It is a cyclic number.

It is not a de Polignac number, because 18271661 - 2² = 18271657 is a prime.

It is a super-3 number, since 3×18271661³ (a number of 23 digits) contains 333 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 (18271663) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 566 + ... + 6071.

It is an arithmetic number, because the mean of its divisors is an integer number (4570263).

Almost surely, 2^18271661 is an apocalyptic number.

It is an amenable number.

18271661 is a deficient number, since it is larger than the sum of its proper divisors (9391).

18271661 is an equidigital number, since it uses as much as digits as its factorization.

18271661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9390.

The product of its digits is 4032, while the sum is 32.

The square root of 18271661 is about 4274.5363491261. The cubic root of 18271661 is about 263.3859936701.

The spelling of 18271661 in words is "eighteen million, two hundred seventy-one thousand, six hundred sixty-one".