261618820 has 12 divisors (see below), whose sum is σ = 549399564. Its totient is φ = 104647520.

The previous prime is 261618817. The next prime is 261618869. The reversal of 261618820 is 28816162.

It can be written as a sum of positive squares in 2 ways, for example, as 195944004 + 65674816 = 13998^2 + 8104^2 .

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 3 ways as a sum of consecutive naturals, for example, 6540451 + ... + 6540490.

It is an arithmetic number, because the mean of its divisors is an integer number (45783297).

Almost surely, 2^261618820 is an apocalyptic number.

261618820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261618820 is an abundant number, since it is smaller than the sum of its proper divisors (287780744).

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

261618820 is a wasteful number, since it uses less digits than its factorization.

261618820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13080950 (or 13080948 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 34.

The square root of 261618820 is about 16174.6350808913. The cubic root of 261618820 is about 639.5723216906.

The spelling of 261618820 in words is "two hundred sixty-one million, six hundred eighteen thousand, eight hundred twenty".