81580813 has 4 divisors (see below), whose sum is σ = 85874560. Its totient is φ = 77287068.

The previous prime is 81580801. The next prime is 81580823. The reversal of 81580813 is 31808518.

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 a cyclic number.

It is not a de Polignac number, because 81580813 - 2²¹ = 79483661 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 (81580823) 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, 2146845 + ... + 2146882.

It is an arithmetic number, because the mean of its divisors is an integer number (21468640).

Almost surely, 2^81580813 is an apocalyptic number.

It is an amenable number.

81580813 is a deficient number, since it is larger than the sum of its proper divisors (4293747).

81580813 is a wasteful number, since it uses less digits than its factorization.

81580813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4293746.

The product of its (nonzero) digits is 7680, while the sum is 34.

The square root of 81580813 is about 9032.2097517717. The cubic root of 81580813 is about 433.7065785500.

The spelling of 81580813 in words is "eighty-one million, five hundred eighty thousand, eight hundred thirteen".