261371440 has 80 divisors (see below), whose sum is σ = 666341280. Its totient is φ = 94556160.

The previous prime is 261371423. The next prime is 261371443. The reversal of 261371440 is 44173162.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 261371399 and 261371408.

It is not an unprimeable number, because it can be changed into a prime (261371443) 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 15 ways as a sum of consecutive naturals, for example, 200872 + ... + 202168.

It is an arithmetic number, because the mean of its divisors is an integer number (8329266).

Almost surely, 2^261371440 is an apocalyptic number.

261371440 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 261371440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (333170640).

261371440 is an abundant number, since it is smaller than the sum of its proper divisors (404969840).

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

261371440 is a wasteful number, since it uses less digits than its factorization.

261371440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1550 (or 1544 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 261371440 is about 16166.9861136824. The cubic root of 261371440 is about 639.3706704283.

The spelling of 261371440 in words is "two hundred sixty-one million, three hundred seventy-one thousand, four hundred forty".