81219644 has 12 divisors (see below), whose sum is σ = 155055768. Its totient is φ = 36918000.

The previous prime is 81219643. The next prime is 81219653. The reversal of 81219644 is 44691218.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81219641) 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, 922907 + ... + 922994.

It is an arithmetic number, because the mean of its divisors is an integer number (12921314).

Almost surely, 2^81219644 is an apocalyptic number.

It is an amenable number.

81219644 is a deficient number, since it is larger than the sum of its proper divisors (73836124).

81219644 is a wasteful number, since it uses less digits than its factorization.

81219644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1845916 (or 1845914 counting only the distinct ones).

The product of its digits is 13824, while the sum is 35.

The square root of 81219644 is about 9012.1941834383. The cubic root of 81219644 is about 433.0656063530.

The spelling of 81219644 in words is "eighty-one million, two hundred nineteen thousand, six hundred forty-four".