261561072 has 80 divisors (see below), whose sum is σ = 689098752. Its totient is φ = 85478400.

The previous prime is 261561067. The next prime is 261561119. The reversal of 261561072 is 270165162.

It is a congruent number.

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, 652072 + ... + 652472.

Almost surely, 2^261561072 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 261561072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (344549376).

261561072 is an abundant number, since it is smaller than the sum of its proper divisors (427537680).

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

261561072 is a wasteful number, since it uses less digits than its factorization.

261561072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 646 (or 640 counting only the distinct ones).

The product of its (nonzero) digits is 5040, while the sum is 30.

The square root of 261561072 is about 16172.8498416327. The cubic root of 261561072 is about 639.5252599129.

The spelling of 261561072 in words is "two hundred sixty-one million, five hundred sixty-one thousand, seventy-two".