81939379 has 4 divisors (see below), whose sum is σ = 81968320. Its totient is φ = 81910440.

The previous prime is 81939373. The next prime is 81939391. The reversal of 81939379 is 97393918.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81939379 - 2⁹ = 81938867 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81939373) 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, 9699 + ... + 16060.

It is an arithmetic number, because the mean of its divisors is an integer number (20492080).

Almost surely, 2^81939379 is an apocalyptic number.

81939379 is a deficient number, since it is larger than the sum of its proper divisors (28941).

81939379 is a wasteful number, since it uses less digits than its factorization.

81939379 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28940.

The product of its digits is 367416, while the sum is 49.

The square root of 81939379 is about 9052.0372845012. The cubic root of 81939379 is about 434.3410625039.

The spelling of 81939379 in words is "eighty-one million, nine hundred thirty-nine thousand, three hundred seventy-nine".