661705261 has 12 divisors (see below), whose sum is σ = 794570880. Its totient is φ = 548878680.

The previous prime is 661705259. The next prime is 661705271. The reversal of 661705261 is 162507166.

It is a happy number.

661705261 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 661705261 - 2¹ = 661705259 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 (661705201) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 216291 + ... + 219328.

It is an arithmetic number, because the mean of its divisors is an integer number (66214240).

Almost surely, 2^661705261 is an apocalyptic number.

It is an amenable number.

661705261 is a deficient number, since it is larger than the sum of its proper divisors (132865619).

661705261 is a wasteful number, since it uses less digits than its factorization.

661705261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 435664 (or 435657 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 661705261 is about 25723.6323445971. The cubic root of 661705261 is about 871.4079729496.

The spelling of 661705261 in words is "six hundred sixty-one million, seven hundred five thousand, two hundred sixty-one".