81100639 has 4 divisors (see below), whose sum is σ = 81137056. Its totient is φ = 81064224.

The previous prime is 81100637. The next prime is 81100651. The reversal of 81100639 is 93600118.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81100639 - 2¹ = 81100637 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 (81100637) 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 3 ways as a sum of consecutive naturals, for example, 14634 + ... + 19399.

It is an arithmetic number, because the mean of its divisors is an integer number (20284264).

Almost surely, 2^81100639 is an apocalyptic number.

81100639 is a deficient number, since it is larger than the sum of its proper divisors (36417).

81100639 is a wasteful number, since it uses less digits than its factorization.

81100639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36416.

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 81100639 is about 9005.5893199723. The cubic root of 81100639 is about 432.8539902073.

The spelling of 81100639 in words is "eighty-one million, one hundred thousand, six hundred thirty-nine".