81955665841 has 9 divisors (see below), whose sum is σ = 95338513899. Its totient is φ = 70245995904.

The previous prime is 81955665833. The next prime is 81955665851. The reversal of 81955665841 is 14856655918.

The square root of 81955665841 is 286279.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 71896378225 + 10059287616 = 268135^2 + 100296^2 .

It is not a de Polignac number, because 81955665841 - 2³ = 81955665833 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81955665811) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1983505 + ... + 2024401.

It is an arithmetic number, because the mean of its divisors is an integer number (10593168211).

Almost surely, 2^81955665841 is an apocalyptic number.

81955665841 is the 286279-th square number.

81955665841 is the 143140-th centered octagonal number.

It is an amenable number.

81955665841 is a deficient number, since it is larger than the sum of its proper divisors (13382848058).

81955665841 is an frugal number, since it uses more digits than its factorization.

81955665841 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81808 (or 40904 counting only the distinct ones).

The product of its digits is 10368000, while the sum is 58.

The spelling of 81955665841 in words is "eighty-one billion, nine hundred fifty-five million, six hundred sixty-five thousand, eight hundred forty-one".