81691627770 has 48 divisors (see below), whose sum is σ = 212927997672. Its totient is φ = 21730099200.

The previous prime is 81691627763. The next prime is 81691627777. The reversal of 81691627770 is 7772619618.

81691627770 is a `hidden beast` number, since 8 + 1 + 6 + 9 + 1 + 627 + 7 + 7 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (81691627763) and next prime (81691627777).

It can be written as a sum of positive squares in 4 ways, for example, as 81689070969 + 2556801 = 285813^2 + 1599^2 .

It is not an unprimeable number, because it can be changed into a prime (81691627777) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1095687 + ... + 1167866.

Almost surely, 2^81691627770 is an apocalyptic number.

81691627770 is an abundant number, since it is smaller than the sum of its proper divisors (131236369902).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81691627770 is a wasteful number, since it uses less digits than its factorization.

81691627770 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2263967 (or 2263964 counting only the distinct ones).

The product of its (nonzero) digits is 1778112, while the sum is 54.

The spelling of 81691627770 in words is "eighty-one billion, six hundred ninety-one million, six hundred twenty-seven thousand, seven hundred seventy".