81638445487 has 4 divisors (see below), whose sum is σ = 82856929816. Its totient is φ = 80419961160.

The previous prime is 81638445463. The next prime is 81638445547. The reversal of 81638445487 is 78454483618.

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 81638445487 - 2⁷ = 81638445359 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 (81638445407) 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 3 ways as a sum of consecutive naturals, for example, 609242064 + ... + 609242197.

It is an arithmetic number, because the mean of its divisors is an integer number (20714232454).

Almost surely, 2^81638445487 is an apocalyptic number.

81638445487 is a deficient number, since it is larger than the sum of its proper divisors (1218484329).

81638445487 is a wasteful number, since it uses less digits than its factorization.

81638445487 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1218484328.

The product of its digits is 20643840, while the sum is 58.

The spelling of 81638445487 in words is "eighty-one billion, six hundred thirty-eight million, four hundred forty-five thousand, four hundred eighty-seven".