1987638913 has 12 divisors (see below), whose sum is σ = 2192914620. Its totient is φ = 1800117696.

The previous prime is 1987638911. The next prime is 1987638941. The reversal of 1987638913 is 3198367891.

It can be written as a sum of positive squares in 6 ways, for example, as 41770369 + 1945868544 = 6463^2 + 44112^2 .

It is not a de Polignac number, because 1987638913 - 2¹ = 1987638911 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1987638911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 101998 + ... + 119911.

It is an arithmetic number, because the mean of its divisors is an integer number (182742885).

Almost surely, 2^1987638913 is an apocalyptic number.

1987638913 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

1987638913 is a deficient number, since it is larger than the sum of its proper divisors (205275707).

1987638913 is a wasteful number, since it uses less digits than its factorization.

1987638913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221988 (or 221975 counting only the distinct ones).

The product of its digits is 1959552, while the sum is 55.

The square root of 1987638913 is about 44582.9441939404. The cubic root of 1987638913 is about 1257.3200182975.

The spelling of 1987638913 in words is "one billion, nine hundred eighty-seven million, six hundred thirty-eight thousand, nine hundred thirteen".