261861440 has 112 divisors (see below), whose sum is σ = 665390592. Its totient is φ = 97929216.

The previous prime is 261861437. The next prime is 261861451. The reversal of 261861440 is 44168162.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 261861397 and 261861406.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 345542 + ... + 346298.

Almost surely, 2^261861440 is an apocalyptic number.

261861440 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 261861440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (332695296).

261861440 is an abundant number, since it is smaller than the sum of its proper divisors (403529152).

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

261861440 is a wasteful number, since it uses less digits than its factorization.

261861440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844 (or 834 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 32.

The square root of 261861440 is about 16182.1333575027. The cubic root of 261861440 is about 639.7699694150.

The spelling of 261861440 in words is "two hundred sixty-one million, eight hundred sixty-one thousand, four hundred forty".