261778 has 16 divisors (see below), whose sum is σ = 436896. Its totient is φ = 116640.

The previous prime is 261773. The next prime is 261787. The reversal of 261778 is 877162.

It is a happy number.

It is a nialpdrome in base 8.

It is a zygodrome in base 8.

It is not an unprimeable number, because it can be changed into a prime (261773) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1525 + ... + 1687.

It is an arithmetic number, because the mean of its divisors is an integer number (27306).

2²⁶¹⁷⁷⁸ is an apocalyptic number.

261778 is a deficient number, since it is larger than the sum of its proper divisors (175118).

261778 is a wasteful number, since it uses less digits than its factorization.

261778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 249.

The product of its digits is 4704, while the sum is 31.

The square root of 261778 is about 511.6424532816. The cubic root of 261778 is about 63.9702009712.

Multiplying 261778 by its sum of digits (31), we get a palindrome (8115118).

The spelling of 261778 in words is "two hundred sixty-one thousand, seven hundred seventy-eight".