• 390 can be written using four 4's:

See also 113.

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390 has 16 divisors (see below), whose sum is σ = 1008. Its totient is φ = 96.

The previous prime is 389. The next prime is 397. The reversal of 390 is 93.

390 is nontrivially palindromic in base 8.

It is an Ulam number.

390 is an undulating number in base 5 and base 8.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 24 + ... + 36.

It is an arithmetic number, because the mean of its divisors is an integer number (63).

2³⁹⁰ is an apocalyptic number.

390 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 390, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (504).

390 is an abundant number, since it is smaller than the sum of its proper divisors (618).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

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

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

The sum of its prime factors is 23.

The product of its (nonzero) digits is 27, while the sum is 12.

The square root of 390 is about 19.7484176581. The cubic root of 390 is about 7.3061435741.

Subtracting from 390 its sum of digits (12), we obtain a triangular number (378 = T₂₇).

Subtracting from 390 its product of nonzero digits (27), we obtain a palindrome (363).

The spelling of 390 in words is "three hundred ninety", and thus it is an aban number and an oban number.