81919008949 has 4 divisors (see below), whose sum is σ = 82113591340. Its totient is φ = 81724426560.

The previous prime is 81919008947. The next prime is 81919009013. The reversal of 81919008949 is 94980091918.

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

It can be written as a sum of positive squares in 2 ways, for example, as 127012900 + 81791996049 = 11270^2 + 285993^2 .

It is a cyclic number.

It is not a de Polignac number, because 81919008949 - 2¹ = 81919008947 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81919008893 and 81919008902.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81919008947) 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, 97290564 + ... + 97291405.

It is an arithmetic number, because the mean of its divisors is an integer number (20528397835).

Almost surely, 2^81919008949 is an apocalyptic number.

It is an amenable number.

81919008949 is a deficient number, since it is larger than the sum of its proper divisors (194582391).

81919008949 is a wasteful number, since it uses less digits than its factorization.

81919008949 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 194582390.

The product of its (nonzero) digits is 1679616, while the sum is 58.

The spelling of 81919008949 in words is "eighty-one billion, nine hundred nineteen million, eight thousand, nine hundred forty-nine".