261797840 has 20 divisors (see below), whose sum is σ = 608680164. Its totient is φ = 104719104.

The previous prime is 261797839. The next prime is 261797843. The reversal of 261797840 is 48797162.

It can be written as a sum of positive squares in 2 ways, for example, as 183439936 + 78357904 = 13544^2 + 8852^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a junction number, because it is equal to n+sod(n) for n = 261797791 and 261797800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261797843) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1636157 + ... + 1636316.

Almost surely, 2^261797840 is an apocalyptic number.

261797840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261797840 is an abundant number, since it is smaller than the sum of its proper divisors (346882324).

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

261797840 is a wasteful number, since it uses less digits than its factorization.

261797840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3272486 (or 3272480 counting only the distinct ones).

The product of its (nonzero) digits is 169344, while the sum is 44.

The square root of 261797840 is about 16180.1681079030. The cubic root of 261797840 is about 639.7181701827.

The spelling of 261797840 in words is "two hundred sixty-one million, seven hundred ninety-seven thousand, eight hundred forty".