261434435221 has 4 divisors (see below), whose sum is σ = 262326703212. Its totient is φ = 260542167232.

The previous prime is 261434435201. The next prime is 261434435231. The reversal of 261434435221 is 122534434162.

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 147940236900 + 113494198321 = 384630^2 + 336889^2 .

It is a cyclic number.

It is not a de Polignac number, because 261434435221 - 2¹⁷ = 261434304149 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261434435201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 446133556 + ... + 446134141.

It is an arithmetic number, because the mean of its divisors is an integer number (65581675803).

Almost surely, 2^261434435221 is an apocalyptic number.

It is an amenable number.

261434435221 is a deficient number, since it is larger than the sum of its proper divisors (892267991).

261434435221 is an equidigital number, since it uses as much as digits as its factorization.

261434435221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 892267990.

The product of its digits is 138240, while the sum is 37.

Adding to 261434435221 its reverse (122534434162), we get a palindrome (383968869383).

The spelling of 261434435221 in words is "two hundred sixty-one billion, four hundred thirty-four million, four hundred thirty-five thousand, two hundred twenty-one".