81938613 has 4 divisors (see below), whose sum is σ = 109251488. Its totient is φ = 54625740.

The previous prime is 81938603. The next prime is 81938617. The reversal of 81938613 is 31683918.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81938613 - 2⁸ = 81938357 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81938617) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13656433 + ... + 13656438.

It is an arithmetic number, because the mean of its divisors is an integer number (27312872).

Almost surely, 2^81938613 is an apocalyptic number.

It is an amenable number.

81938613 is a deficient number, since it is larger than the sum of its proper divisors (27312875).

81938613 is a wasteful number, since it uses less digits than its factorization.

81938613 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27312874.

The product of its digits is 31104, while the sum is 39.

The square root of 81938613 is about 9051.9949734851. The cubic root of 81938613 is about 434.3397090387.

The spelling of 81938613 in words is "eighty-one million, nine hundred thirty-eight thousand, six hundred thirteen".