261644540 has 24 divisors (see below), whose sum is σ = 554897952. Its totient is φ = 103620800.

The previous prime is 261644531. The next prime is 261644543. The reversal of 261644540 is 45446162.

It is a zygodrome in base 2.

It is a junction number, because it is equal to n+sod(n) for n = 261644497 and 261644506.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261644543) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 62744 + ... + 66783.

It is an arithmetic number, because the mean of its divisors is an integer number (23120748).

Almost surely, 2^261644540 is an apocalyptic number.

261644540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261644540 is an abundant number, since it is smaller than the sum of its proper divisors (293253412).

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

261644540 is a wasteful number, since it uses less digits than its factorization.

261644540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129637 (or 129635 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 32.

The square root of 261644540 is about 16175.4301333844. The cubic root of 261644540 is about 639.5932799956.

The spelling of 261644540 in words is "two hundred sixty-one million, six hundred forty-four thousand, five hundred forty".