309840 has 40 divisors (see below), whose sum is σ = 961248. Its totient is φ = 82560.

The previous prime is 309823. The next prime is 309851. The reversal of 309840 is 48903.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 309840.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 309840.

It is an unprimeable number.

309840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 406 + ... + 885.

2³⁰⁹⁸⁴⁰ is an apocalyptic number.

309840 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

309840 is an abundant number, since it is smaller than the sum of its proper divisors (651408).

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

309840 is a wasteful number, since it uses less digits than its factorization.

309840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1307 (or 1301 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 309840 is about 556.6327334967. The cubic root of 309840 is about 67.6673488193.

It can be divided in two parts, 309 and 840, that multiplied together give a triangular number (259560 = T₇₂₀).

The spelling of 309840 in words is "three hundred nine thousand, eight hundred forty".