655 has 4 divisors (see below), whose sum is σ = 792. Its totient is φ = 520.

The previous prime is 653. The next prime is 659. The reversal of 655 is 556.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 655 - 2¹ = 653 is a prime.

It is a Duffinian number.

655 is a lucky number.

It is a plaindrome in base 12, base 14 and base 16.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (653) 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, 61 + ... + 70.

It is an arithmetic number, because the mean of its divisors is an integer number (198).

655 is a deficient number, since it is larger than the sum of its proper divisors (137).

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

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

The sum of its prime factors is 136.

The product of its digits is 150, while the sum is 16.

The square root of 655 is about 25.5929677841. The cubic root of 655 is about 8.6845456027.

Subtracting from 655 its product of digits (150), we obtain a palindrome (505).

Subtracting from 655 its reverse (556), we obtain a palindrome (99).

It can be divided in two parts, 65 and 5, that multiplied together give a triangular number (325 = T₂₅).

The spelling of 655 in words is "six hundred fifty-five", and thus it is an aban number and an oban number.