261836661 has 4 divisors (see below), whose sum is σ = 349115552. Its totient is φ = 174557772.

The previous prime is 261836647. The next prime is 261836693. The reversal of 261836661 is 166638162.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 261836661 - 2⁵ = 261836629 is a prime.

It is a super-3 number, since 3×261836661³ (a number of 26 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261837661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 43639441 + ... + 43639446.

It is an arithmetic number, because the mean of its divisors is an integer number (87278888).

Almost surely, 2^261836661 is an apocalyptic number.

It is an amenable number.

261836661 is a deficient number, since it is larger than the sum of its proper divisors (87278891).

261836661 is an equidigital number, since it uses as much as digits as its factorization.

261836661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87278890.

The product of its digits is 62208, while the sum is 39.

The square root of 261836661 is about 16181.3677110435. The cubic root of 261836661 is about 639.7497890732.

The spelling of 261836661 in words is "two hundred sixty-one million, eight hundred thirty-six thousand, six hundred sixty-one".