• 27 can be written using four 4's:

• Deleting all the even digits from 2^{27} = 134217728 we obtain a prime (13177).

27 has 4 divisors (see below), whose sum is σ = 40. Its totient is φ = 18.

The previous prime is 23. The next prime is 29. The reversal of 27 is 72.

The cubic root of 27 is 3.

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

27 is nontrivially palindromic in base 2 and base 8.

27 is an esthetic number in base 4, base 6, base 12 and base 13, because in such bases its adjacent digits differ by 1.

27 is an astonishing number since 27 = 2 + ... + 7.

It is not a de Polignac number, because 27 - 2^{2} = 23 is a prime.

It is a Smith number, since the sum of its digits (9) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 3 = 27 / (2 + 7).

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

27 is a nontrivial repdigit in base 8.

It is a plaindrome in base 4, base 7, base 8, base 10, base 11, base 12, base 14, base 15 and base 16.

It is a nialpdrome in base 3, base 6, base 8, base 9 and base 13.

It is a zygodrome in base 8.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8 + 9 + 10.

It is an arithmetic number, because the mean of its divisors is an integer number (10).

27 is the 3-rd decagonal number.

27 is a deficient number, since it is larger than the sum of its proper divisors (13).

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

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

The sum of its prime factors is 9 (or 3 counting only the distinct ones).

The product of its digits is 14, while the sum is 9.

The square root of 27 is about 5.1961524227.

Multiplying 27 by its product of digits (14), we get a triangular number (378 = T_{27}).

Adding to 27 its reverse (72), we get a palindrome (99).

Subtracting 27 from its reverse (72), we obtain a triangular number (45 = T_{9}).

The spelling of 27 in words is "twenty-seven", and thus it is an aban number, an iban number, an oban number, and an uban number.

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