81439891 has 8 divisors (see below), whose sum is σ = 88482240. Its totient is φ = 74508672.

The previous prime is 81439889. The next prime is 81439901. The reversal of 81439891 is 19893418.

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 81439891 - 2¹ = 81439889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81439811) 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, 26251 + ... + 29188.

It is an arithmetic number, because the mean of its divisors is an integer number (11060280).

Almost surely, 2^81439891 is an apocalyptic number.

81439891 is a deficient number, since it is larger than the sum of its proper divisors (7042349).

81439891 is a wasteful number, since it uses less digits than its factorization.

81439891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55565.

The product of its digits is 62208, while the sum is 43.

The square root of 81439891 is about 9024.4052989657. The cubic root of 81439891 is about 433.4567076058.

The spelling of 81439891 in words is "eighty-one million, four hundred thirty-nine thousand, eight hundred ninety-one".