261329820 has 24 divisors (see below), whose sum is σ = 731723664. Its totient is φ = 69687936.

The previous prime is 261329807. The next prime is 261329837. The reversal of 261329820 is 28923162.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2177689 + ... + 2177808.

It is an arithmetic number, because the mean of its divisors is an integer number (30488486).

Almost surely, 2^261329820 is an apocalyptic number.

261329820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261329820 is an abundant number, since it is smaller than the sum of its proper divisors (470393844).

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

261329820 is a wasteful number, since it uses less digits than its factorization.

261329820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4355509 (or 4355507 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 261329820 is about 16165.6988713758. The cubic root of 261329820 is about 639.3367314742.

The spelling of 261329820 in words is "two hundred sixty-one million, three hundred twenty-nine thousand, eight hundred twenty".