81215442 has 108 divisors (see below), whose sum is σ = 225292158. Its totient is φ = 21067200.

The previous prime is 81215371. The next prime is 81215467. The reversal of 81215442 is 24451218.

81215442 is a `hidden beast` number, since 8 + 1 + 215 + 442 = 666.

It can be written as a sum of positive squares in only one way, i.e., 81162081 + 53361 = 9009^2 + 231^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 106342 + ... + 107102.

Almost surely, 2^81215442 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81215442, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (112646079).

81215442 is an abundant number, since it is smaller than the sum of its proper divisors (144076716).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81215442 is a wasteful number, since it uses less digits than its factorization.

81215442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 805 (or 784 counting only the distinct ones).

The product of its digits is 2560, while the sum is 27.

The square root of 81215442 is about 9011.9610518466. The cubic root of 81215442 is about 433.0581378271.

The spelling of 81215442 in words is "eighty-one million, two hundred fifteen thousand, four hundred forty-two".