81494221 has 4 divisors (see below), whose sum is σ = 85037472. Its totient is φ = 77950972.

The previous prime is 81494219. The next prime is 81494227. The reversal of 81494221 is 12249418.

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 81494221 - 2¹ = 81494219 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81494227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1771591 + ... + 1771636.

It is an arithmetic number, because the mean of its divisors is an integer number (21259368).

Almost surely, 2^81494221 is an apocalyptic number.

It is an amenable number.

81494221 is a deficient number, since it is larger than the sum of its proper divisors (3543251).

81494221 is a wasteful number, since it uses less digits than its factorization.

81494221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3543250.

The product of its digits is 4608, while the sum is 31.

The square root of 81494221 is about 9027.4149677524. The cubic root of 81494221 is about 433.5530750730.

The spelling of 81494221 in words is "eighty-one million, four hundred ninety-four thousand, two hundred twenty-one".