81391835 has 64 divisors (see below), whose sum is σ = 125971200. Its totient is φ = 49201152.

The previous prime is 81391831. The next prime is 81391841. The reversal of 81391835 is 53819318.

It is not a de Polignac number, because 81391835 - 2² = 81391831 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81391831) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 914471 + ... + 914559.

It is an arithmetic number, because the mean of its divisors is an integer number (1968300).

Almost surely, 2^81391835 is an apocalyptic number.

81391835 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

81391835 is a deficient number, since it is larger than the sum of its proper divisors (44579365).

81391835 is a wasteful number, since it uses less digits than its factorization.

81391835 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 200.

The product of its digits is 25920, while the sum is 38.

The square root of 81391835 is about 9021.7423483493. The cubic root of 81391835 is about 433.3714328763.

The spelling of 81391835 in words is "eighty-one million, three hundred ninety-one thousand, eight hundred thirty-five".