81649443 has 24 divisors (see below), whose sum is σ = 113885184. Its totient is φ = 52027920.

The previous prime is 81649429. The next prime is 81649489. The reversal of 81649443 is 34494618.

It is a happy number.

It is not a de Polignac number, because 81649443 - 2⁵ = 81649411 is a prime.

Its product of digits (82944) is a multiple of the sum of its prime divisors (384).

It is not an unprimeable number, because it can be changed into a prime (81642443) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 366030 + ... + 366252.

It is an arithmetic number, because the mean of its divisors is an integer number (4745216).

Almost surely, 2^81649443 is an apocalyptic number.

81649443 is a deficient number, since it is larger than the sum of its proper divisors (32235741).

81649443 is a wasteful number, since it uses less digits than its factorization.

81649443 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 415 (or 384 counting only the distinct ones).

The product of its digits is 82944, while the sum is 39.

The square root of 81649443 is about 9036.0081341265. The cubic root of 81649443 is about 433.8281632649.

The spelling of 81649443 in words is "eighty-one million, six hundred forty-nine thousand, four hundred forty-three".