261231645 has 24 divisors (see below), whose sum is σ = 425259936. Its totient is φ = 136934752.

The previous prime is 261231629. The next prime is 261231667. The reversal of 261231645 is 546132162.

It is not a de Polignac number, because 261231645 - 2⁴ = 261231629 is a prime.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 49714 + ... + 54716.

It is an arithmetic number, because the mean of its divisors is an integer number (17719164).

Almost surely, 2^261231645 is an apocalyptic number.

It is an amenable number.

261231645 is a deficient number, since it is larger than the sum of its proper divisors (164028291).

261231645 is an equidigital number, since it uses as much as digits as its factorization.

261231645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5129 (or 5070 counting only the distinct ones).

The product of its digits is 8640, while the sum is 30.

The square root of 261231645 is about 16162.6620641527. The cubic root of 261231645 is about 639.2566605697.

The spelling of 261231645 in words is "two hundred sixty-one million, two hundred thirty-one thousand, six hundred forty-five".