261291660 has 48 divisors (see below), whose sum is σ = 836134656. Its totient is φ = 59723712.

The previous prime is 261291623. The next prime is 261291671. The reversal of 261291660 is 66192162.

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 310642 + ... + 311481.

It is an arithmetic number, because the mean of its divisors is an integer number (17419472).

Almost surely, 2^261291660 is an apocalyptic number.

261291660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261291660 is an abundant number, since it is smaller than the sum of its proper divisors (574842996).

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

261291660 is a wasteful number, since it uses less digits than its factorization.

261291660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 622142 (or 622140 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 33.

The square root of 261291660 is about 16164.5185514447. The cubic root of 261291660 is about 639.3056108042.

The spelling of 261291660 in words is "two hundred sixty-one million, two hundred ninety-one thousand, six hundred sixty".