81993739969 has 2 divisors, whose sum is σ = 81993739970. Its totient is φ = 81993739968.

The previous prime is 81993739963. The next prime is 81993739987. The reversal of 81993739969 is 96993739918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 53922412944 + 28071327025 = 232212^2 + 167545^2 .

It is a cyclic number.

It is not a de Polignac number, because 81993739969 - 2⁵ = 81993739937 is a prime.

It is a super-2 number, since 2×81993739969² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81993739963) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40996869984 + 40996869985.

It is an arithmetic number, because the mean of its divisors is an integer number (40996869985).

Almost surely, 2^81993739969 is an apocalyptic number.

It is an amenable number.

81993739969 is a deficient number, since it is larger than the sum of its proper divisors (1).

81993739969 is an equidigital number, since it uses as much as digits as its factorization.

81993739969 is an evil number, because the sum of its binary digits is even.

The product of its digits is 178564176, while the sum is 73.

The spelling of 81993739969 in words is "eighty-one billion, nine hundred ninety-three million, seven hundred thirty-nine thousand, nine hundred sixty-nine".