261189840 has 80 divisors (see below), whose sum is σ = 844910208. Its totient is φ = 66620928.

The previous prime is 261189829. The next prime is 261189881. The reversal of 261189840 is 48981162.

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

It is a congruent number.

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, 18139 + ... + 29178.

Almost surely, 2^261189840 is an apocalyptic number.

261189840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261189840 is an abundant number, since it is smaller than the sum of its proper divisors (583720368).

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

261189840 is a wasteful number, since it uses less digits than its factorization.

261189840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47356 (or 47350 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 39.

The square root of 261189840 is about 16161.3687539144. The cubic root of 261189840 is about 639.2225585879. Note that the first 3 decimals are identical.

The spelling of 261189840 in words is "two hundred sixty-one million, one hundred eighty-nine thousand, eight hundred forty".