649840 has 20 divisors (see below), whose sum is σ = 1511064. Its totient is φ = 259904.

The previous prime is 649829. The next prime is 649843. The reversal of 649840 is 48946.

649840 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 (20).

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (649843) 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, 3982 + ... + 4141.

2⁶⁴⁹⁸⁴⁰ is an apocalyptic number.

It is an amenable number.

649840 is an abundant number, since it is smaller than the sum of its proper divisors (861224).

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

649840 is a wasteful number, since it uses less digits than its factorization.

649840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8136 (or 8130 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 31.

The square root of 649840 is about 806.1265409351. The cubic root of 649840 is about 86.6168023479.

The spelling of 649840 in words is "six hundred forty-nine thousand, eight hundred forty".