81399738 has 64 divisors (see below), whose sum is σ = 194273280. Its totient is φ = 22248000.

The previous prime is 81399733. The next prime is 81399739. The reversal of 81399738 is 83799318.

It is not an unprimeable number, because it can be changed into a prime (81399733) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 131193 + ... + 131811.

It is an arithmetic number, because the mean of its divisors is an integer number (3035520).

Almost surely, 2^81399738 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81399738, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (97136640).

81399738 is an abundant number, since it is smaller than the sum of its proper divisors (112873542).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81399738 is a wasteful number, since it uses less digits than its factorization.

81399738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 763.

The product of its digits is 326592, while the sum is 48.

The square root of 81399738 is about 9022.1803351518. The cubic root of 81399738 is about 433.3854589498.

The spelling of 81399738 in words is "eighty-one million, three hundred ninety-nine thousand, seven hundred thirty-eight".