261220320 has 144 divisors (see below), whose sum is σ = 895959792. Its totient is φ = 69304320.

The previous prime is 261220319. The next prime is 261220367. The reversal of 261220320 is 23022162.

261220320 is a `hidden beast` number, since 2 + 612 + 20 + 32 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-3 number, since 3×261220320³ (a number of 26 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 261220293 and 261220302.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 407200 + ... + 407840.

It is an arithmetic number, because the mean of its divisors is an integer number (6221943).

Almost surely, 2^261220320 is an apocalyptic number.

261220320 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 261220320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (447979896).

261220320 is an abundant number, since it is smaller than the sum of its proper divisors (634739472).

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

261220320 is a wasteful number, since it uses less digits than its factorization.

261220320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 945 (or 934 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 261220320 is about 16162.3117158407. The cubic root of 261220320 is about 639.2474226813.

Adding to 261220320 its reverse (23022162), we get a palindrome (284242482).

The spelling of 261220320 in words is "two hundred sixty-one million, two hundred twenty thousand, three hundred twenty".