781680091 has 4 divisors (see below), whose sum is σ = 781737832. Its totient is φ = 781622352.

The previous prime is 781680059. The next prime is 781680113. The reversal of 781680091 is 190086187.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 781680091 - 2⁵ = 781680059 is a prime.

It is a super-2 number, since 2×781680091² = 1222047529331536562, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (781680191) 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, 3640 + ... + 39706.

It is an arithmetic number, because the mean of its divisors is an integer number (195434458).

Almost surely, 2^781680091 is an apocalyptic number.

781680091 is a deficient number, since it is larger than the sum of its proper divisors (57741).

781680091 is a wasteful number, since it uses less digits than its factorization.

781680091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57740.

The product of its (nonzero) digits is 24192, while the sum is 40.

The square root of 781680091 is about 27958.5423618614. The cubic root of 781680091 is about 921.1768536597.

The spelling of 781680091 in words is "seven hundred eighty-one million, six hundred eighty thousand, ninety-one".