87999991 has 4 divisors (see below), whose sum is σ = 88266184. Its totient is φ = 87733800.

The previous prime is 87999971. The next prime is 87999997. The reversal of 87999991 is 19999978.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 87999991 - 2¹⁷ = 87868919 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 (87999997) 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, 132600 + ... + 133261.

It is an arithmetic number, because the mean of its divisors is an integer number (22066546).

Almost surely, 2^87999991 is an apocalyptic number.

87999991 is a deficient number, since it is larger than the sum of its proper divisors (266193).

87999991 is a wasteful number, since it uses less digits than its factorization.

87999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 266192.

The product of its digits is 3306744, while the sum is 61.

The square root of 87999991 is about 9380.8310399452. The cubic root of 87999991 is about 444.7960029504.

The spelling of 87999991 in words is "eighty-seven million, nine hundred ninety-nine thousand, nine hundred ninety-one".