81931945069 has 8 divisors (see below), whose sum is σ = 88296167960. Its totient is φ = 75576545856.

The previous prime is 81931945061. The next prime is 81931945079. The reversal of 81931945069 is 96054913918.

It can be written as a sum of positive squares in 4 ways, for example, as 324900 + 81931620169 = 570^2 + 286237^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81931945069 - 2³ = 81931945061 is a prime.

It is a super-2 number, since 2×81931945069² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81931945061) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2186622 + ... + 2223775.

It is an arithmetic number, because the mean of its divisors is an integer number (11037020995).

Almost surely, 2^81931945069 is an apocalyptic number.

It is an amenable number.

81931945069 is a deficient number, since it is larger than the sum of its proper divisors (6364222891).

81931945069 is a wasteful number, since it uses less digits than its factorization.

81931945069 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4411839.

The product of its (nonzero) digits is 2099520, while the sum is 55.

The spelling of 81931945069 in words is "eighty-one billion, nine hundred thirty-one million, nine hundred forty-five thousand, sixty-nine".