81632221 has 16 divisors (see below), whose sum is σ = 93316608. Its totient is φ = 70686000.

The previous prime is 81632219. The next prime is 81632233. The reversal of 81632221 is 12223618.

It is not a de Polignac number, because 81632221 - 2¹ = 81632219 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81632251) 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, 77146 + ... + 78196.

It is an arithmetic number, because the mean of its divisors is an integer number (5832288).

Almost surely, 2^81632221 is an apocalyptic number.

It is an amenable number.

81632221 is a deficient number, since it is larger than the sum of its proper divisors (11684387).

81632221 is a wasteful number, since it uses less digits than its factorization.

81632221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1392.

The product of its digits is 1152, while the sum is 25.

The square root of 81632221 is about 9035.0551188136. The cubic root of 81632221 is about 433.7976592234.

Adding to 81632221 its reverse (12223618), we get a palindrome (93855839).

The spelling of 81632221 in words is "eighty-one million, six hundred thirty-two thousand, two hundred twenty-one".