261625665 has 64 divisors (see below), whose sum is σ = 511819776. Its totient is φ = 111393792.

The previous prime is 261625627. The next prime is 261625697. The reversal of 261625665 is 566526162.

It is a happy number.

It is not a de Polignac number, because 261625665 - 2⁶ = 261625601 is a prime.

It is a Curzon 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 63 ways as a sum of consecutive naturals, for example, 183144 + ... + 184566.

It is an arithmetic number, because the mean of its divisors is an integer number (7997184).

Almost surely, 2^261625665 is an apocalyptic number.

It is an amenable number.

261625665 is a deficient number, since it is larger than the sum of its proper divisors (250194111).

261625665 is a wasteful number, since it uses less digits than its factorization.

261625665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1558.

The product of its digits is 129600, while the sum is 39.

The square root of 261625665 is about 16174.8466762440. The cubic root of 261625665 is about 639.5778995696.

The spelling of 261625665 in words is "two hundred sixty-one million, six hundred twenty-five thousand, six hundred sixty-five".