781995561 has 16 divisors (see below), whose sum is σ = 1090492416. Its totient is φ = 497518736.

The previous prime is 781995509. The next prime is 781995587. The reversal of 781995561 is 165599187.

781995561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 781995561 - 2⁶ = 781995497 is a prime.

It is a super-2 number, since 2×781995561² = 1223034114847409442, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (781995961) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17776 + ... + 43358.

It is an arithmetic number, because the mean of its divisors is an integer number (68155776).

Almost surely, 2^781995561 is an apocalyptic number.

It is an amenable number.

781995561 is a deficient number, since it is larger than the sum of its proper divisors (308496855).

781995561 is a wasteful number, since it uses less digits than its factorization.

781995561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26052.

The product of its digits is 680400, while the sum is 51.

The square root of 781995561 is about 27964.1835389485. The cubic root of 781995561 is about 921.3007596669.

The spelling of 781995561 in words is "seven hundred eighty-one million, nine hundred ninety-five thousand, five hundred sixty-one".