81479221 has 4 divisors (see below), whose sum is σ = 81739852. Its totient is φ = 81218592.

The previous prime is 81479213. The next prime is 81479227. The reversal of 81479221 is 12297418.

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 2464900 + 79014321 = 1570^2 + 8889^2 .

It is a cyclic number.

It is not a de Polignac number, because 81479221 - 2³ = 81479213 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 (81479227) 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, 129846 + ... + 130471.

It is an arithmetic number, because the mean of its divisors is an integer number (20434963).

Almost surely, 2^81479221 is an apocalyptic number.

It is an amenable number.

81479221 is a deficient number, since it is larger than the sum of its proper divisors (260631).

81479221 is a wasteful number, since it uses less digits than its factorization.

81479221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 260630.

The product of its digits is 8064, while the sum is 34.

The square root of 81479221 is about 9026.5841268998. The cubic root of 81479221 is about 433.5264732064.

The spelling of 81479221 in words is "eighty-one million, four hundred seventy-nine thousand, two hundred twenty-one".