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393 = 3131

393 has 4 divisors (see below), whose sum is σ = 528. Its totient is φ = 260.

The previous prime is 389. The next prime is 397.

393 is nontrivially palindromic in base 4 and base 10.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (389) and next prime (397).

It is a cyclic number.

It is not a de Polignac number, because 393 - 22 = 389 is a prime.

It is a D-number.

393 is an undulating number in base 10.

It is a Curzon number.

393 is a lucky number.

It is a plaindrome in base 12 and base 16.

It is a nialpdrome in base 8.

It is not an unprimeable number, because it can be changed into a prime (397) 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, 63 + ... + 68.

It is an arithmetic number, because the mean of its divisors is an integer number (132).

It is an amenable number.

393 is a deficient number, since it is larger than the sum of its proper divisors (135).

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

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

The sum of its prime factors is 134.

The product of its digits is 81, while the sum is 15.

The square root of 393 is about 19.8242276016. The cubic root of 393 is about 7.3248294446.

Subtracting from 393 its sum of digits (15), we obtain a triangular number (378 = T27).

Adding to 393 its product of digits (81), we get a palindrome (474).

The spelling of 393 in words is "three hundred ninety-three", and thus it is an aban number and an oban number.

Divisors: 1 3 131 393