655640 has 32 divisors (see below), whose sum is σ = 1518480. Its totient is φ = 254592.

The previous prime is 655637. The next prime is 655643. The reversal of 655640 is 46556.

It is an interprime number because it is at equal distance from previous prime (655637) and next prime (655643).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (655643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1259 + ... + 1701.

2⁶⁵⁵⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 655640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (759240).

655640 is an abundant number, since it is smaller than the sum of its proper divisors (862840).

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

655640 is a wasteful number, since it uses less digits than its factorization.

655640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 491 (or 487 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 655640 is about 809.7159995949. The cubic root of 655640 is about 86.8737323625.

The spelling of 655640 in words is "six hundred fifty-five thousand, six hundred forty".