81879721357 has 16 divisors (see below), whose sum is σ = 95931297792. Its totient is φ = 68428122480.

The previous prime is 81879721327. The next prime is 81879721397. The reversal of 81879721357 is 75312797818.

It is a cyclic number.

It is not a de Polignac number, because 81879721357 - 2³¹ = 79732237709 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 (81879721307) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 386619 + ... + 559672.

It is an arithmetic number, because the mean of its divisors is an integer number (5995706112).

Almost surely, 2^81879721357 is an apocalyptic number.

It is an amenable number.

81879721357 is a deficient number, since it is larger than the sum of its proper divisors (14051576435).

81879721357 is a wasteful number, since it uses less digits than its factorization.

81879721357 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 946608.

The product of its digits is 5927040, while the sum is 58.

The spelling of 81879721357 in words is "eighty-one billion, eight hundred seventy-nine million, seven hundred twenty-one thousand, three hundred fifty-seven".