81993432739 has 4 divisors (see below), whose sum is σ = 82130317200. Its totient is φ = 81856548280.

The previous prime is 81993432709. The next prime is 81993432749. The reversal of 81993432739 is 93723439918.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81993432739 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81993432709) 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, 68441332 + ... + 68442529.

It is an arithmetic number, because the mean of its divisors is an integer number (20532579300).

Almost surely, 2^81993432739 is an apocalyptic number.

81993432739 is a deficient number, since it is larger than the sum of its proper divisors (136884461).

81993432739 is a wasteful number, since it uses less digits than its factorization.

81993432739 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136884460.

The product of its digits is 8817984, while the sum is 58.

The spelling of 81993432739 in words is "eighty-one billion, nine hundred ninety-three million, four hundred thirty-two thousand, seven hundred thirty-nine".