81652221 has 24 divisors (see below), whose sum is σ = 137007104. Its totient is φ = 45891360.

The previous prime is 81652217. The next prime is 81652243. The reversal of 81652221 is 12225618.

It is a happy number.

81652221 is a `hidden beast` number, since 8 + 1 + 652 + 2 + 2 + 1 = 666.

It is not a de Polignac number, because 81652221 - 2² = 81652217 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 (81652261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6781 + ... + 14466.

Almost surely, 2^81652221 is an apocalyptic number.

It is an amenable number.

81652221 is a deficient number, since it is larger than the sum of its proper divisors (55354883).

81652221 is a wasteful number, since it uses less digits than its factorization.

81652221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21321 (or 21318 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 81652221 is about 9036.1618511401. The cubic root of 81652221 is about 433.8330833270.

Adding to 81652221 its reverse (12225618), we get a palindrome (93877839).

The spelling of 81652221 in words is "eighty-one million, six hundred fifty-two thousand, two hundred twenty-one".