261325440 has 240 divisors, whose sum is σ = 946569690. Its totient is φ = 68705280.

The previous prime is 261325439. The next prime is 261325451. The reversal of 261325440 is 44523162.

261325440 is a `hidden beast` number, since 2 + 613 + 2 + 5 + 4 + 40 = 666.

It can be written as a sum of positive squares in only one way, i.e., 235192896 + 26132544 = 15336^2 + 5112^2 .

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 3680605 + ... + 3680675.

Almost surely, 2^261325440 is an apocalyptic number.

261325440 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 261325440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (473284845).

261325440 is an abundant number, since it is smaller than the sum of its proper divisors (685244250).

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

261325440 is an frugal number, since it uses more digits than its factorization.

261325440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173 (or 81 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

The square root of 261325440 is about 16165.5633987808. The cubic root of 261325440 is about 639.3331596015. Note that the first 3 decimals are identical.

Multiplying 261325440 by its product of nonzero digits (5760), we get a square (1505234534400 = 1226880²).

261325440 divided by its product of nonzero digits (5760) gives a square (45369 = 213²).

The spelling of 261325440 in words is "two hundred sixty-one million, three hundred twenty-five thousand, four hundred forty".