81221206 has 16 divisors (see below), whose sum is σ = 140726160. Its totient is φ = 34746880.

The previous prime is 81221201. The next prime is 81221207. The reversal of 81221206 is 60212218.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81221201) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 108211 + ... + 108958.

It is an arithmetic number, because the mean of its divisors is an integer number (8795385).

Almost surely, 2^81221206 is an apocalyptic number.

81221206 is a deficient number, since it is larger than the sum of its proper divisors (59504954).

81221206 is a wasteful number, since it uses less digits than its factorization.

81221206 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 217199.

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 81221206 is about 9012.2808433825. The cubic root of 81221206 is about 433.0683825457.

The spelling of 81221206 in words is "eighty-one million, two hundred twenty-one thousand, two hundred six".