261439920 has 160 divisors (see below), whose sum is σ = 1029219840. Its totient is φ = 59754240.

The previous prime is 261439909. The next prime is 261439921. The reversal of 261439920 is 29934162.

261439920 is a `hidden beast` number, since 2 + 614 + 39 + 9 + 2 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (261439921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6475 + ... + 23765.

It is an arithmetic number, because the mean of its divisors is an integer number (6432624).

Almost surely, 2^261439920 is an apocalyptic number.

261439920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261439920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (514609920).

261439920 is an abundant number, since it is smaller than the sum of its proper divisors (767779920).

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

261439920 is a wasteful number, since it uses less digits than its factorization.

261439920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17320 (or 17308 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 36.

The square root of 261439920 is about 16169.1038712725. The cubic root of 261439920 is about 639.4265044809.

It can be divided in two parts, 26143 and 9920, that added together give a palindrome (36063).

The spelling of 261439920 in words is "two hundred sixty-one million, four hundred thirty-nine thousand, nine hundred twenty".