261511440 has 80 divisors (see below), whose sum is σ = 853368000. Its totient is φ = 66064896.

The previous prime is 261511427. The next prime is 261511451. The reversal of 261511440 is 44115162.

It is a happy number.

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

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 261511440.

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, 24115 + ... + 33234.

It is an arithmetic number, because the mean of its divisors is an integer number (10667100).

Almost surely, 2^261511440 is an apocalyptic number.

261511440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261511440 is an abundant number, since it is smaller than the sum of its proper divisors (591856560).

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

261511440 is a wasteful number, since it uses less digits than its factorization.

261511440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57384 (or 57378 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 24.

The square root of 261511440 is about 16171.3153453886. The cubic root of 261511440 is about 639.4848067403.

The spelling of 261511440 in words is "two hundred sixty-one million, five hundred eleven thousand, four hundred forty".