81399123 has 12 divisors (see below), whose sum is σ = 126621040. Its totient is φ = 50091696.

The previous prime is 81399107. The next prime is 81399127. The reversal of 81399123 is 32199318.

It is not a de Polignac number, because 81399123 - 2⁴ = 81399107 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81399127) 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 11 ways as a sum of consecutive naturals, for example, 347743 + ... + 347976.

Almost surely, 2^81399123 is an apocalyptic number.

81399123 is a deficient number, since it is larger than the sum of its proper divisors (45221917).

81399123 is a wasteful number, since it uses less digits than its factorization.

81399123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 695738 (or 695735 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 81399123 is about 9022.1462524169. The cubic root of 81399123 is about 433.3843674937.

The spelling of 81399123 in words is "eighty-one million, three hundred ninety-nine thousand, one hundred twenty-three".