261521680 has 40 divisors (see below), whose sum is σ = 694901952. Its totient is φ = 89664384.

The previous prime is 261521647. The next prime is 261521683. The reversal of 261521680 is 86125162.

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×261521680² = 136787178220044800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (261521683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 232942 + ... + 234061.

Almost surely, 2^261521680 is an apocalyptic number.

261521680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261521680 is an abundant number, since it is smaller than the sum of its proper divisors (433380272).

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

261521680 is a wasteful number, since it uses less digits than its factorization.

261521680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 467023 (or 467017 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 31.

The square root of 261521680 is about 16171.6319522799. The cubic root of 261521680 is about 639.4931533974.

The spelling of 261521680 in words is "two hundred sixty-one million, five hundred twenty-one thousand, six hundred eighty".