81205887 has 48 divisors (see below), whose sum is σ = 133626240. Its totient is φ = 43662528.

The previous prime is 81205877. The next prime is 81205897. The reversal of 81205887 is 78850218.

It is an interprime number because it is at equal distance from previous prime (81205877) and next prime (81205897).

It is not a de Polignac number, because 81205887 - 2¹⁰ = 81204863 is a prime.

It is a hoax number, since the sum of its digits (39) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81205877) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 183088 + ... + 183530.

It is an arithmetic number, because the mean of its divisors is an integer number (2783880).

Almost surely, 2^81205887 is an apocalyptic number.

81205887 is a gapful number since it is divisible by the number (87) formed by its first and last digit.

81205887 is a deficient number, since it is larger than the sum of its proper divisors (52420353).

81205887 is a wasteful number, since it uses less digits than its factorization.

81205887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 532 (or 525 counting only the distinct ones).

The product of its (nonzero) digits is 35840, while the sum is 39.

The square root of 81205887 is about 9011.4309074641. The cubic root of 81205887 is about 433.0411540586.

The spelling of 81205887 in words is "eighty-one million, two hundred five thousand, eight hundred eighty-seven".