1987776777891 has 8 divisors (see below), whose sum is σ = 2653109857024. Its totient is φ = 1323814108680.

The previous prime is 1987776777871. The next prime is 1987776777893.

It is a happy number.

1987776777891 is nontrivially palindromic in base 10.

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

It is not a de Polignac number, because 1987776777891 - 2⁵ = 1987776777859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1987776777893) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 342599095 + ... + 342604896.

It is an arithmetic number, because the mean of its divisors is an integer number (331638732128).

Almost surely, 2^{1987776777891} is an apocalyptic number.

1987776777891 is a deficient number, since it is larger than the sum of its proper divisors (665333079133).

1987776777891 is an equidigital number, since it uses as much as digits as its factorization.

1987776777891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 685204961.

The product of its digits is 3659354496, while the sum is 84.

The spelling of 1987776777891 in words is "one trillion, nine hundred eighty-seven billion, seven hundred seventy-six million, seven hundred seventy-seven thousand, eight hundred ninety-one".