• 87 can be written using four 4's:
87 has 4 divisors (see below), whose sum is σ = 120. Its totient is φ = 56.
The previous prime is 83. The next prime is 89. The reversal of 87 is 78.
87 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.
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 87 - 22 = 83 is a prime.
It is an Ulam number.
It is a D-number.
It is an alternating number because its digits alternate between even and odd.
87 is a lucky number.
It is a plaindrome in base 4, base 6, base 8, base 11, base 13, base 15 and base 16.
It is a nialpdrome in base 5, base 10, base 12 and base 14.
It is a congruent number.
It is a pernicious number, because its binary representation contains a prime number (5) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12 + ... + 17.
It is an arithmetic number, because the mean of its divisors is an integer number (30).
87 is a deficient number, since it is larger than the sum of its proper divisors (33).
87 is a wasteful number, since it uses less digits than its factorization.
87 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 32.
The product of its digits is 56, while the sum is 15.
The square root of 87 is about 9.3273790531. The cubic root of 87 is about 4.4310476217.
Multiplying 87 by its reverse (78), we get a triangular number (6786 = T116).
The spelling of 87 in words is "eighty-seven", and thus it is an aban number, an oban number, and an uban number.
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