987971991 has 16 divisors (see below), whose sum is σ = 1334914560. Its totient is φ = 649859840.

The previous prime is 987971987. The next prime is 987972019. The reversal of 987971991 is 199179789.

It is a cyclic number.

It is not a de Polignac number, because 987971991 - 2² = 987971987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (987971911) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 229186 + ... + 233456.

It is an arithmetic number, because the mean of its divisors is an integer number (83432160).

Almost surely, 2^987971991 is an apocalyptic number.

987971991 is a deficient number, since it is larger than the sum of its proper divisors (346942569).

987971991 is a wasteful number, since it uses less digits than its factorization.

987971991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5286.

The product of its digits is 2571912, while the sum is 60.

The square root of 987971991 is about 31432.0217453475. The cubic root of 987971991 is about 995.9744806045.

The spelling of 987971991 in words is "nine hundred eighty-seven million, nine hundred seventy-one thousand, nine hundred ninety-one".