81938813 has 8 divisors (see below), whose sum is σ = 91290240. Its totient is φ = 72904480.

The previous prime is 81938807. The next prime is 81938821. The reversal of 81938813 is 31883918.

It is a happy number.

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

It is not a de Polignac number, because 81938813 - 2¹⁶ = 81873277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81938863) 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, 78728 + ... + 79761.

It is an arithmetic number, because the mean of its divisors is an integer number (11411280).

Almost surely, 2^81938813 is an apocalyptic number.

It is an amenable number.

81938813 is a deficient number, since it is larger than the sum of its proper divisors (9351427).

81938813 is a wasteful number, since it uses less digits than its factorization.

81938813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158547.

The product of its digits is 41472, while the sum is 41.

The square root of 81938813 is about 9052.0060207669. The cubic root of 81938813 is about 434.3400624247.

The spelling of 81938813 in words is "eighty-one million, nine hundred thirty-eight thousand, eight hundred thirteen".