261988128 has 96 divisors (see below), whose sum is σ = 767188800. Its totient is φ = 86980608.

The previous prime is 261988081. The next prime is 261988141. The reversal of 261988128 is 821889162.

It is a happy number.

261988128 is a `hidden beast` number, since 2 + 619 + 8 + 8 + 1 + 28 = 666.

It is a tau number, because it is divible by the number of its divisors (96).

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 304563 + ... + 305421.

It is an arithmetic number, because the mean of its divisors is an integer number (7991550).

Almost surely, 2^261988128 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261988128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (383594400).

261988128 is an abundant number, since it is smaller than the sum of its proper divisors (505200672).

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

261988128 is a wasteful number, since it uses less digits than its factorization.

261988128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1231 (or 1217 counting only the distinct ones).

The product of its digits is 110592, while the sum is 45.

The square root of 261988128 is about 16186.0473247795. The cubic root of 261988128 is about 639.8731258917.

The spelling of 261988128 in words is "two hundred sixty-one million, nine hundred eighty-eight thousand, one hundred twenty-eight".