261489816 has 128 divisors (see below), whose sum is σ = 836006400. Its totient is φ = 74183040.

The previous prime is 261489793. The next prime is 261489817. The reversal of 261489816 is 618984162.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261489817) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 245926 + ... + 246986.

It is an arithmetic number, because the mean of its divisors is an integer number (6531300).

Almost surely, 2^261489816 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 261489816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (418003200).

261489816 is an abundant number, since it is smaller than the sum of its proper divisors (574516584).

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

261489816 is a wasteful number, since it uses less digits than its factorization.

261489816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1246 (or 1236 counting only the distinct ones).

The product of its digits is 165888, while the sum is 45.

The square root of 261489816 is about 16170.6467403131. The cubic root of 261489816 is about 639.4671802321.

The spelling of 261489816 in words is "two hundred sixty-one million, four hundred eighty-nine thousand, eight hundred sixteen".