261665250401 has 16 divisors (see below), whose sum is σ = 286958039040. Its totient is φ = 237493105920.

The previous prime is 261665250359. The next prime is 261665250443. The reversal of 261665250401 is 104052566162.

It is an interprime number because it is at equal distance from previous prime (261665250359) and next prime (261665250443).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261665250401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261665250901) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 86816 + ... + 728606.

It is an arithmetic number, because the mean of its divisors is an integer number (17934877440).

Almost surely, 2^261665250401 is an apocalyptic number.

It is an amenable number.

261665250401 is a deficient number, since it is larger than the sum of its proper divisors (25292788639).

261665250401 is a wasteful number, since it uses less digits than its factorization.

261665250401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 642664.

The product of its (nonzero) digits is 86400, while the sum is 38.

The spelling of 261665250401 in words is "two hundred sixty-one billion, six hundred sixty-five million, two hundred fifty thousand, four hundred one".