405639 has 12 divisors (see below), whose sum is σ = 631176. Its totient is φ = 249552.

The previous prime is 405611. The next prime is 405641. The reversal of 405639 is 936504.

It is a happy number.

It is not a de Polignac number, because 405639 - 2⁵ = 405607 is a prime.

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

405639 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (405659) 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, 1617 + ... + 1850.

It is an arithmetic number, because the mean of its divisors is an integer number (52598).

2⁴⁰⁵⁶³⁹ is an apocalyptic number.

405639 is a deficient number, since it is larger than the sum of its proper divisors (225537).

405639 is a wasteful number, since it uses less digits than its factorization.

405639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3486 (or 3483 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 27.

The square root of 405639 is about 636.8979510094. The cubic root of 405639 is about 74.0252531294.

It can be divided in two parts, 4056 and 39, that added together give a triangular number (4095 = T₉₀).

The spelling of 405639 in words is "four hundred five thousand, six hundred thirty-nine".