81643995983 has 32 divisors (see below), whose sum is σ = 96701299200. Its totient is φ = 68087900160.

The previous prime is 81643995973. The next prime is 81643995997. The reversal of 81643995983 is 38959934618.

It is a cyclic number.

It is not a de Polignac number, because 81643995983 - 2⁴ = 81643995967 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81643995913) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3905543 + ... + 3926391.

It is an arithmetic number, because the mean of its divisors is an integer number (3021915600).

Almost surely, 2^81643995983 is an apocalyptic number.

81643995983 is a deficient number, since it is larger than the sum of its proper divisors (15057303217).

81643995983 is a wasteful number, since it uses less digits than its factorization.

81643995983 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21407.

The product of its digits is 50388480, while the sum is 65.

The spelling of 81643995983 in words is "eighty-one billion, six hundred forty-three million, nine hundred ninety-five thousand, nine hundred eighty-three".