83991987 has 24 divisors (see below), whose sum is σ = 124001280. Its totient is φ = 54768240.

The previous prime is 83991979. The next prime is 83991997. The reversal of 83991987 is 78919938.

It is not a de Polignac number, because 83991987 - 2³ = 83991979 is a prime.

It is not an unprimeable number, because it can be changed into a prime (83991967) 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 23 ways as a sum of consecutive naturals, for example, 194662 + ... + 195092.

It is an arithmetic number, because the mean of its divisors is an integer number (5166720).

Almost surely, 2^83991987 is an apocalyptic number.

83991987 is a deficient number, since it is larger than the sum of its proper divisors (40009293).

83991987 is a wasteful number, since it uses less digits than its factorization.

83991987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 863 (or 860 counting only the distinct ones).

The product of its digits is 979776, while the sum is 54.

The square root of 83991987 is about 9164.7142344974. The cubic root of 83991987 is about 437.9379877178.

The spelling of 83991987 in words is "eighty-three million, nine hundred ninety-one thousand, nine hundred eighty-seven".