81924412817 has 4 divisors (see below), whose sum is σ = 88226290740. Its totient is φ = 75622534896.

The previous prime is 81924412723. The next prime is 81924412883. The reversal of 81924412817 is 71821442918.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 71821442918 = 2 ⋅35910721459.

It can be written as a sum of positive squares in 2 ways, for example, as 6962901136 + 74961511681 = 83444^2 + 273791^2 .

It is a cyclic number.

It is not a de Polignac number, because 81924412817 - 2¹⁸ = 81924150673 is a prime.

It is a super-4 number, since 4×81924412817⁴ (a number of 45 digits) contains 4444 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81924412897) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3150938942 + ... + 3150938967.

It is an arithmetic number, because the mean of its divisors is an integer number (22056572685).

Almost surely, 2^81924412817 is an apocalyptic number.

It is an amenable number.

81924412817 is a deficient number, since it is larger than the sum of its proper divisors (6301877923).

81924412817 is a wasteful number, since it uses less digits than its factorization.

81924412817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6301877922.

The product of its digits is 258048, while the sum is 47.

The spelling of 81924412817 in words is "eighty-one billion, nine hundred twenty-four million, four hundred twelve thousand, eight hundred seventeen".