961656581 has 4 divisors (see below), whose sum is σ = 961915500. Its totient is φ = 961397664.

The previous prime is 961656547. The next prime is 961656649. The reversal of 961656581 is 185656169.

961656581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 792422500 + 169234081 = 28150^2 + 13009^2 .

It is a cyclic number.

It is not a de Polignac number, because 961656581 - 2¹⁸ = 961394437 is a prime.

It is a super-2 number, since 2×961656581² = 1849566759561219122, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (961656881) 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, 123806 + ... + 131343.

It is an arithmetic number, because the mean of its divisors is an integer number (240478875).

Almost surely, 2^961656581 is an apocalyptic number.

It is an amenable number.

961656581 is a deficient number, since it is larger than the sum of its proper divisors (258919).

961656581 is a wasteful number, since it uses less digits than its factorization.

961656581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 258918.

The product of its digits is 388800, while the sum is 47.

The square root of 961656581 is about 31010.5882079009. The cubic root of 961656581 is about 987.0519314460.

The spelling of 961656581 in words is "nine hundred sixty-one million, six hundred fifty-six thousand, five hundred eighty-one".