261561641 has 8 divisors (see below), whose sum is σ = 286991424. Its totient is φ = 236407120.

The previous prime is 261561637. The next prime is 261561661. The reversal of 261561641 is 146165162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 261561641 - 2² = 261561637 is a prime.

It is a super-2 number, since 2×261561641² = 136828984085225762, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 261561598 and 261561607.

It is not an unprimeable number, because it can be changed into a prime (261561611) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 66821 + ... + 70626.

It is an arithmetic number, because the mean of its divisors is an integer number (35873928).

Almost surely, 2^261561641 is an apocalyptic number.

It is an amenable number.

261561641 is a deficient number, since it is larger than the sum of its proper divisors (25429783).

261561641 is a wasteful number, since it uses less digits than its factorization.

261561641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137631.

The product of its digits is 8640, while the sum is 32.

The square root of 261561641 is about 16172.8674328333. The cubic root of 261561641 is about 639.5257236537.

The spelling of 261561641 in words is "two hundred sixty-one million, five hundred sixty-one thousand, six hundred forty-one".