81398887 has 4 divisors (see below), whose sum is σ = 81433440. Its totient is φ = 81364336.

The previous prime is 81398881. The next prime is 81398893. The reversal of 81398887 is 78889318.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 78889318 = 2 ⋅39444659.

It is an interprime number because it is at equal distance from previous prime (81398881) and next prime (81398893).

It is a cyclic number.

It is not a de Polignac number, because 81398887 - 2³ = 81398879 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 (81398881) 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, 13462 + ... + 18547.

It is an arithmetic number, because the mean of its divisors is an integer number (20358360).

Almost surely, 2^81398887 is an apocalyptic number.

81398887 is a deficient number, since it is larger than the sum of its proper divisors (34553).

81398887 is a wasteful number, since it uses less digits than its factorization.

81398887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34552.

The product of its digits is 774144, while the sum is 52.

The square root of 81398887 is about 9022.1331734795. The cubic root of 81398887 is about 433.3839486570.

The spelling of 81398887 in words is "eighty-one million, three hundred ninety-eight thousand, eight hundred eighty-seven".