81731994 has 8 divisors (see below), whose sum is σ = 163464000. Its totient is φ = 27243996.

The previous prime is 81731981. The next prime is 81732029. The reversal of 81731994 is 49913718.

It is a happy number.

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

81731994 is an admirable number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6810994 + ... + 6811005.

It is an arithmetic number, because the mean of its divisors is an integer number (20433000).

Almost surely, 2^81731994 is an apocalyptic number.

81731994 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

81731994 is a wasteful number, since it uses less digits than its factorization.

81731994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13622004.

The product of its digits is 54432, while the sum is 42.

The square root of 81731994 is about 9040.5748711019. The cubic root of 81731994 is about 433.9743201551.

The spelling of 81731994 in words is "eighty-one million, seven hundred thirty-one thousand, nine hundred ninety-four".