81558813 has 16 divisors (see below), whose sum is σ = 125513856. Its totient is φ = 46142400.

The previous prime is 81558797. The next prime is 81558823. The reversal of 81558813 is 31885518.

It is not a de Polignac number, because 81558813 - 2⁴ = 81558797 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81558823) 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, 17106 + ... + 21347.

It is an arithmetic number, because the mean of its divisors is an integer number (7844616).

Almost surely, 2^81558813 is an apocalyptic number.

It is an amenable number.

81558813 is a deficient number, since it is larger than the sum of its proper divisors (43955043).

81558813 is a wasteful number, since it uses less digits than its factorization.

81558813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38564.

The product of its digits is 38400, while the sum is 39.

The square root of 81558813 is about 9030.9918059978. The cubic root of 81558813 is about 433.6675889796.

The spelling of 81558813 in words is "eighty-one million, five hundred fifty-eight thousand, eight hundred thirteen".