671728581 has 12 divisors (see below), whose sum is σ = 972055552. Its totient is φ = 446997096.

The previous prime is 671728571. The next prime is 671728591. The reversal of 671728581 is 185827176.

It is a happy number.

671728581 is a `hidden beast` number, since 67 + 1 + 7 + 2 + 8 + 581 = 666.

It is an interprime number because it is at equal distance from previous prime (671728571) and next prime (671728591).

It is not a de Polignac number, because 671728581 - 2⁵ = 671728549 is a prime.

It is a super-2 number, since 2×671728581² = 902438573064547122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (671728571) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 63301 + ... + 73146.

Almost surely, 2^671728581 is an apocalyptic number.

It is an amenable number.

671728581 is a deficient number, since it is larger than the sum of its proper divisors (300326971).

671728581 is a wasteful number, since it uses less digits than its factorization.

671728581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137000 (or 136997 counting only the distinct ones).

The product of its digits is 188160, while the sum is 45.

The square root of 671728581 is about 25917.7271572953. The cubic root of 671728581 is about 875.7858870275.

The spelling of 671728581 in words is "six hundred seventy-one million, seven hundred twenty-eight thousand, five hundred eighty-one".