81187939 has 8 divisors (see below), whose sum is σ = 92951648. Its totient is φ = 69465600.

The previous prime is 81187921. The next prime is 81187943. The reversal of 81187939 is 93978118.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81187939 - 2¹¹ = 81185891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81187919) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6012 + ... + 14089.

It is an arithmetic number, because the mean of its divisors is an integer number (11618956).

Almost surely, 2^81187939 is an apocalyptic number.

81187939 is a deficient number, since it is larger than the sum of its proper divisors (11763709).

81187939 is a wasteful number, since it uses less digits than its factorization.

81187939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20685.

The product of its digits is 108864, while the sum is 46.

The square root of 81187939 is about 9010.4350061470. The cubic root of 81187939 is about 433.0092483450.

The spelling of 81187939 in words is "eighty-one million, one hundred eighty-seven thousand, nine hundred thirty-nine".