81666819964 has 24 divisors (see below), whose sum is σ = 143950514400. Its totient is φ = 40539163584.

The previous prime is 81666819961. The next prime is 81666819967. The reversal of 81666819964 is 46991866618.

It is an interprime number because it is at equal distance from previous prime (81666819961) and next prime (81666819967).

It is a super-2 number, since 2×81666819964² (a number of 23 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81666819896 and 81666819905.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81666819961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175762 + ... + 440710.

It is an arithmetic number, because the mean of its divisors is an integer number (5997938100).

Almost surely, 2^81666819964 is an apocalyptic number.

It is an amenable number.

81666819964 is a deficient number, since it is larger than the sum of its proper divisors (62283694436).

81666819964 is a wasteful number, since it uses less digits than its factorization.

81666819964 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 265509 (or 265507 counting only the distinct ones).

The product of its digits is 26873856, while the sum is 64.

The spelling of 81666819964 in words is "eighty-one billion, six hundred sixty-six million, eight hundred nineteen thousand, nine hundred sixty-four".