640620 has 36 divisors (see below), whose sum is σ = 1943760. Its totient is φ = 170784.

The previous prime is 640613. The next prime is 640621. The reversal of 640620 is 26046.

640620 is a `hidden beast` number, since 6 + 40 + 620 = 666.

640620 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 640593 and 640602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640621) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1600 + ... + 1959.

2⁶⁴⁰⁶²⁰ is an apocalyptic number.

640620 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640620 is an abundant number, since it is smaller than the sum of its proper divisors (1303140).

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

640620 is a wasteful number, since it uses less digits than its factorization.

640620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3574 (or 3569 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 640620 is about 800.3874061978. The cubic root of 640620 is about 86.2052067347.

Adding to 640620 its reverse (26046), we get a palindrome (666666).

The spelling of 640620 in words is "six hundred forty thousand, six hundred twenty".