671666391 has 16 divisors (see below), whose sum is σ = 1085521920. Its totient is φ = 407070360.

The previous prime is 671666371. The next prime is 671666431. The reversal of 671666391 is 193666176.

It is not a de Polignac number, because 671666391 - 2⁶ = 671666327 is a prime.

It is a super-2 number, since 2×671666391² = 902271481597929762, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (671666351) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1130455 + ... + 1131048.

It is an arithmetic number, because the mean of its divisors is an integer number (67845120).

Almost surely, 2^671666391 is an apocalyptic number.

671666391 is a deficient number, since it is larger than the sum of its proper divisors (413855529).

671666391 is a wasteful number, since it uses less digits than its factorization.

671666391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2261523 (or 2261517 counting only the distinct ones).

The product of its digits is 244944, while the sum is 45.

The square root of 671666391 is about 25916.5273715442. The cubic root of 671666391 is about 875.7588588464.

The spelling of 671666391 in words is "six hundred seventy-one million, six hundred sixty-six thousand, three hundred ninety-one".