261504991 has 8 divisors (see below), whose sum is σ = 285704064. Its totient is φ = 237376920.

The previous prime is 261504989. The next prime is 261505019. The reversal of 261504991 is 199405162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 261504991 - 2¹ = 261504989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 261504991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261504941) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9891 + ... + 24916.

It is an arithmetic number, because the mean of its divisors is an integer number (35713008).

Almost surely, 2^261504991 is an apocalyptic number.

261504991 is a deficient number, since it is larger than the sum of its proper divisors (24199073).

261504991 is a wasteful number, since it uses less digits than its factorization.

261504991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35501.

The product of its (nonzero) digits is 19440, while the sum is 37.

The square root of 261504991 is about 16171.1159478868. The cubic root of 261504991 is about 639.4795500277.

The spelling of 261504991 in words is "two hundred sixty-one million, five hundred four thousand, nine hundred ninety-one".