261365640 has 64 divisors (see below), whose sum is σ = 785160000. Its totient is φ = 69603072.

The previous prime is 261365639. The next prime is 261365647. The reversal of 261365640 is 46563162.

261365640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (261365647) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 173611 + ... + 175109.

It is an arithmetic number, because the mean of its divisors is an integer number (12268125).

Almost surely, 2^261365640 is an apocalyptic number.

261365640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261365640 is an abundant number, since it is smaller than the sum of its proper divisors (523794360).

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

261365640 is a wasteful number, since it uses less digits than its factorization.

261365640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2966 (or 2962 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 33.

The square root of 261365640 is about 16166.8067347884. The cubic root of 261365640 is about 639.3659410448.

The spelling of 261365640 in words is "two hundred sixty-one million, three hundred sixty-five thousand, six hundred forty".