81640462381 has 2 divisors, whose sum is σ = 81640462382. Its totient is φ = 81640462380.

The previous prime is 81640462327. The next prime is 81640462459. The reversal of 81640462381 is 18326404618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 44665018281 + 36975444100 = 211341^2 + 192290^2 .

It is a cyclic number.

It is not a de Polignac number, because 81640462381 - 2¹¹ = 81640460333 is a prime.

It is a super-2 number, since 2×81640462381² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81640462681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40820231190 + 40820231191.

It is an arithmetic number, because the mean of its divisors is an integer number (40820231191).

Almost surely, 2^81640462381 is an apocalyptic number.

It is an amenable number.

81640462381 is a deficient number, since it is larger than the sum of its proper divisors (1).

81640462381 is an equidigital number, since it uses as much as digits as its factorization.

81640462381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 221184, while the sum is 43.

Adding to 81640462381 its reverse (18326404618), we get a palindrome (99966866999).

The spelling of 81640462381 in words is "eighty-one billion, six hundred forty million, four hundred sixty-two thousand, three hundred eighty-one".