640980 has 48 divisors (see below), whose sum is σ = 1995840. Its totient is φ = 170784.

The previous prime is 640973. The next prime is 640993. The reversal of 640980 is 89046.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54 + ... + 1133.

It is an arithmetic number, because the mean of its divisors is an integer number (41580).

2⁶⁴⁰⁹⁸⁰ is an apocalyptic number.

640980 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (997920).

640980 is an abundant number, since it is smaller than the sum of its proper divisors (1354860).

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

640980 is a wasteful number, since it uses less digits than its factorization.

640980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1205 (or 1197 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 640980 is about 800.6122657067. The cubic root of 640980 is about 86.2213515439.

The spelling of 640980 in words is "six hundred forty thousand, nine hundred eighty".