81580821 has 16 divisors (see below), whose sum is σ = 124444800. Its totient is φ = 46568448.

The previous prime is 81580801. The next prime is 81580823. The reversal of 81580821 is 12808518.

It is not a de Polignac number, because 81580821 - 2⁶ = 81580757 is a prime.

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 15 ways as a sum of consecutive naturals, for example, 29965 + ... + 32573.

It is an arithmetic number, because the mean of its divisors is an integer number (7777800).

Almost surely, 2^81580821 is an apocalyptic number.

It is an amenable number.

81580821 is a deficient number, since it is larger than the sum of its proper divisors (42863979).

81580821 is a wasteful number, since it uses less digits than its factorization.

81580821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4108.

The product of its (nonzero) digits is 5120, while the sum is 33.

The square root of 81580821 is about 9032.2101946312. The cubic root of 81580821 is about 433.7065927267.

The spelling of 81580821 in words is "eighty-one million, five hundred eighty thousand, eight hundred twenty-one".