77781891 has 8 divisors (see below), whose sum is σ = 113137344. Its totient is φ = 47140520.

The previous prime is 77781889. The next prime is 77781923. The reversal of 77781891 is 19818777.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 77781891 - 2¹ = 77781889 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 77781891.

It is not an unprimeable number, because it can be changed into a prime (77781811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1178481 + ... + 1178546.

It is an arithmetic number, because the mean of its divisors is an integer number (14142168).

Almost surely, 2^77781891 is an apocalyptic number.

77781891 is a deficient number, since it is larger than the sum of its proper divisors (35355453).

77781891 is a wasteful number, since it uses less digits than its factorization.

77781891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2357041.

The product of its digits is 197568, while the sum is 48.

The square root of 77781891 is about 8819.4042315794. The cubic root of 77781891 is about 426.8672462537.

It can be divided in two parts, 7778 and 1891, that added together give a palindrome (9669).

The spelling of 77781891 in words is "seventy-seven million, seven hundred eighty-one thousand, eight hundred ninety-one".