81355138577 has 8 divisors (see below), whose sum is σ = 81728753064. Its totient is φ = 80982177408.

The previous prime is 81355138567. The next prime is 81355138589. The reversal of 81355138577 is 77583155318.

It can be written as a sum of positive squares in 4 ways, for example, as 11111057281 + 70244081296 = 105409^2 + 265036^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 81355138577 - 2⁴ = 81355138561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81355138507) 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, 87173 + ... + 412685.

It is an arithmetic number, because the mean of its divisors is an integer number (10216094133).

Almost surely, 2^81355138577 is an apocalyptic number.

It is an amenable number.

81355138577 is a deficient number, since it is larger than the sum of its proper divisors (373614487).

81355138577 is a wasteful number, since it uses less digits than its factorization.

81355138577 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 326659.

The product of its digits is 3528000, while the sum is 53.

The spelling of 81355138577 in words is "eighty-one billion, three hundred fifty-five million, one hundred thirty-eight thousand, five hundred seventy-seven".