261756961 has 4 divisors (see below), whose sum is σ = 261792000. Its totient is φ = 261721924.

The previous prime is 261756949. The next prime is 261756991. The reversal of 261756961 is 169657162.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 169657162 = 2 ⋅84828581.

It is a cyclic number.

It is not a de Polignac number, because 261756961 - 2¹⁵ = 261724193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261756931) 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, 1321 + ... + 22918.

It is an arithmetic number, because the mean of its divisors is an integer number (65448000).

Almost surely, 2^261756961 is an apocalyptic number.

It is an amenable number.

261756961 is a deficient number, since it is larger than the sum of its proper divisors (35039).

261756961 is a wasteful number, since it uses less digits than its factorization.

261756961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35038.

The product of its digits is 136080, while the sum is 43.

The square root of 261756961 is about 16178.9048146035. The cubic root of 261756961 is about 639.6848717156.

The spelling of 261756961 in words is "two hundred sixty-one million, seven hundred fifty-six thousand, nine hundred sixty-one".