261639 has 12 divisors (see below), whose sum is σ = 432016. Its totient is φ = 149472.

The previous prime is 261637. The next prime is 261641. The reversal of 261639 is 936162.

It is a happy number.

261639 is a `hidden beast` number, since 26 + 1 + 639 = 666.

261639 is digitally balanced in base 7, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (261637) and next prime (261641).

It is not a de Polignac number, because 261639 - 2¹ = 261637 is a prime.

It is a Duffinian number.

261639 is strictly pandigital in base 7.

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261631) 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, 2014 + ... + 2139.

2²⁶¹⁶³⁹ is an apocalyptic number.

261639 is a deficient number, since it is larger than the sum of its proper divisors (170377).

261639 is a wasteful number, since it uses less digits than its factorization.

261639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4166 (or 4163 counting only the distinct ones).

The product of its digits is 1944, while the sum is 27.

The square root of 261639 is about 511.5065981979. The cubic root of 261639 is about 63.9588765765.

It can be divided in two parts, 261 and 639, that added together give a square (900 = 30²).

The spelling of 261639 in words is "two hundred sixty-one thousand, six hundred thirty-nine".