261601111 has 4 divisors (see below), whose sum is σ = 261848272. Its totient is φ = 261353952.

The previous prime is 261601097. The next prime is 261601129. The reversal of 261601111 is 111106162.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 111106162 = 2 ⋅55553081.

It is a cyclic number.

It is not a de Polignac number, because 261601111 - 2⁵ = 261601079 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261601511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 121986 + ... + 124111.

It is an arithmetic number, because the mean of its divisors is an integer number (65462068).

Almost surely, 2^261601111 is an apocalyptic number.

261601111 is a deficient number, since it is larger than the sum of its proper divisors (247161).

261601111 is a wasteful number, since it uses less digits than its factorization.

261601111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247160.

The product of its (nonzero) digits is 72, while the sum is 19.

The square root of 261601111 is about 16174.0876404204. The cubic root of 261601111 is about 639.5578904635.

Adding to 261601111 its reverse (111106162), we get a palindrome (372707273).

The spelling of 261601111 in words is "two hundred sixty-one million, six hundred one thousand, one hundred eleven".