261635220 has 288 divisors, whose sum is σ = 1014773760. Its totient is φ = 52980480.

The previous prime is 261635203. The next prime is 261635233. The reversal of 261635220 is 22536162.

261635220 is a `hidden beast` number, since 2 + 6 + 1 + 635 + 2 + 20 = 666.

261635220 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 595761 + ... + 596199.

It is an arithmetic number, because the mean of its divisors is an integer number (3523520).

Almost surely, 2^261635220 is an apocalyptic number.

261635220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261635220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (507386880).

261635220 is an abundant number, since it is smaller than the sum of its proper divisors (753138540).

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

261635220 is a wasteful number, since it uses less digits than its factorization.

261635220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 515 (or 510 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 261635220 is about 16175.1420395618. The cubic root of 261635220 is about 639.5856856208.

The spelling of 261635220 in words is "two hundred sixty-one million, six hundred thirty-five thousand, two hundred twenty".