261891801 has 24 divisors (see below), whose sum is σ = 407469920. Its totient is φ = 161554176.

The previous prime is 261891797. The next prime is 261891821. The reversal of 261891801 is 108198162.

It is not a de Polignac number, because 261891801 - 2² = 261891797 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261891821) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10456 + ... + 25161.

Almost surely, 2^261891801 is an apocalyptic number.

It is an amenable number.

261891801 is a deficient number, since it is larger than the sum of its proper divisors (145578119).

261891801 is a wasteful number, since it uses less digits than its factorization.

261891801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35685 (or 35682 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 36.

The square root of 261891801 is about 16183.0714328276. The cubic root of 261891801 is about 639.7946940752.

The spelling of 261891801 in words is "two hundred sixty-one million, eight hundred ninety-one thousand, eight hundred one".