1987117813 has 4 divisors (see below), whose sum is σ = 1987229740. Its totient is φ = 1987005888.

The previous prime is 1987117807. The next prime is 1987117823. The reversal of 1987117813 is 3187117891.

It is a happy number.

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 can be written as a sum of positive squares in 2 ways, for example, as 1239532849 + 747584964 = 35207^2 + 27342^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1987117813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1987117823) 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, 22770 + ... + 67027.

It is an arithmetic number, because the mean of its divisors is an integer number (496807435).

Almost surely, 2^1987117813 is an apocalyptic number.

It is an amenable number.

1987117813 is a deficient number, since it is larger than the sum of its proper divisors (111927).

1987117813 is an equidigital number, since it uses as much as digits as its factorization.

1987117813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111926.

The product of its digits is 84672, while the sum is 46.

The square root of 1987117813 is about 44577.0996476891. The cubic root of 1987117813 is about 1257.2101313486.

The spelling of 1987117813 in words is "one billion, nine hundred eighty-seven million, one hundred seventeen thousand, eight hundred thirteen".