81723620057 has 4 divisors (see below), whose sum is σ = 81724990116. Its totient is φ = 81722250000.

The previous prime is 81723620003. The next prime is 81723620071. The reversal of 81723620057 is 75002632718.

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

It can be written as a sum of positive squares in 2 ways, for example, as 44725482256 + 36998137801 = 211484^2 + 192349^2 .

It is a cyclic number.

It is not a de Polignac number, because 81723620057 - 2³⁰ = 80649878233 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81723619996 and 81723620023.

It is not an unprimeable number, because it can be changed into a prime (81723620557) 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, 591278 + ... + 716279.

It is an arithmetic number, because the mean of its divisors is an integer number (20431247529).

Almost surely, 2^81723620057 is an apocalyptic number.

It is an amenable number.

81723620057 is a deficient number, since it is larger than the sum of its proper divisors (1370059).

81723620057 is a wasteful number, since it uses less digits than its factorization.

81723620057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1370058.

The product of its (nonzero) digits is 141120, while the sum is 41.

The spelling of 81723620057 in words is "eighty-one billion, seven hundred twenty-three million, six hundred twenty thousand, fifty-seven".