81666672 has 20 divisors (see below), whose sum is σ = 210972360. Its totient is φ = 27222208.

The previous prime is 81666671. The next prime is 81666701. The reversal of 81666672 is 27666618.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81666671) 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, 850647 + ... + 850742.

It is an arithmetic number, because the mean of its divisors is an integer number (10548618).

Almost surely, 2^81666672 is an apocalyptic number.

It is an amenable number.

81666672 is an abundant number, since it is smaller than the sum of its proper divisors (129305688).

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

81666672 is a wasteful number, since it uses less digits than its factorization.

81666672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1701400 (or 1701394 counting only the distinct ones).

The product of its digits is 145152, while the sum is 42.

The square root of 81666672 is about 9036.9614362351. The cubic root of 81666672 is about 433.8586754133.

The spelling of 81666672 in words is "eighty-one million, six hundred sixty-six thousand, six hundred seventy-two".