87705991 has 4 divisors (see below), whose sum is σ = 87740352. Its totient is φ = 87671632.

The previous prime is 87705979. The next prime is 87705997. The reversal of 87705991 is 19950778.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19950778 = 2 ⋅9975389.

It is a cyclic number.

It is not a de Polignac number, because 87705991 - 2²¹ = 85608839 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 (87705997) 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 3 ways as a sum of consecutive naturals, for example, 13015 + ... + 18568.

It is an arithmetic number, because the mean of its divisors is an integer number (21935088).

Almost surely, 2^87705991 is an apocalyptic number.

87705991 is a deficient number, since it is larger than the sum of its proper divisors (34361).

87705991 is a wasteful number, since it uses less digits than its factorization.

87705991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34360.

The product of its (nonzero) digits is 158760, while the sum is 46.

The square root of 87705991 is about 9365.1476763583. The cubic root of 87705991 is about 444.3001092404.

It can be divided in two parts, 877059 and 91, that added together give a triangular number (877150 = T₁₃₂₄).

The spelling of 87705991 in words is "eighty-seven million, seven hundred five thousand, nine hundred ninety-one".