261506491 has 8 divisors (see below), whose sum is σ = 268913840. Its totient is φ = 254117088.

The previous prime is 261506459. The next prime is 261506501. The reversal of 261506491 is 194605162.

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 261506491 - 2⁵ = 261506459 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261506411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28420 + ... + 36478.

It is an arithmetic number, because the mean of its divisors is an integer number (33614230).

Almost surely, 2^261506491 is an apocalyptic number.

261506491 is a deficient number, since it is larger than the sum of its proper divisors (7407349).

261506491 is an equidigital number, since it uses as much as digits as its factorization.

261506491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8973.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 261506491 is about 16171.1623268088. The cubic root of 261506491 is about 639.4807727163.

The spelling of 261506491 in words is "two hundred sixty-one million, five hundred six thousand, four hundred ninety-one".