261021161641 has 4 divisors (see below), whose sum is σ = 261071276500. Its totient is φ = 260971046784.

The previous prime is 261021161627. The next prime is 261021161683. The reversal of 261021161641 is 146161120162.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 243045056016 + 17976105625 = 492996^2 + 134075^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261021161641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261021101641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25049616 + ... + 25060033.

It is an arithmetic number, because the mean of its divisors is an integer number (65267819125).

Almost surely, 2^261021161641 is an apocalyptic number.

It is an amenable number.

261021161641 is a deficient number, since it is larger than the sum of its proper divisors (50114859).

261021161641 is an equidigital number, since it uses as much as digits as its factorization.

261021161641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50114858.

The product of its (nonzero) digits is 3456, while the sum is 31.

The spelling of 261021161641 in words is "two hundred sixty-one billion, twenty-one million, one hundred sixty-one thousand, six hundred forty-one".