261685491 has 4 divisors (see below), whose sum is σ = 348913992. Its totient is φ = 174456992.

The previous prime is 261685483. The next prime is 261685507. The reversal of 261685491 is 194586162.

261685491 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 261685491 - 2³ = 261685483 is a prime.

It is a super-2 number, since 2×261685491² = 136958592399822162, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (261685091) 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, 43614246 + ... + 43614251.

It is an arithmetic number, because the mean of its divisors is an integer number (87228498).

Almost surely, 2^261685491 is an apocalyptic number.

261685491 is a deficient number, since it is larger than the sum of its proper divisors (87228501).

261685491 is an equidigital number, since it uses as much as digits as its factorization.

261685491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87228500.

The product of its digits is 103680, while the sum is 42.

The square root of 261685491 is about 16176.6959234573. The cubic root of 261685491 is about 639.6266466618.

The spelling of 261685491 in words is "two hundred sixty-one million, six hundred eighty-five thousand, four hundred ninety-one".