671663561 has 4 divisors (see below), whose sum is σ = 671716500. Its totient is φ = 671610624.

The previous prime is 671663539. The next prime is 671663563. The reversal of 671663561 is 165366176.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 546671161 + 124992400 = 23381^2 + 11180^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-671663561 is a prime.

It is a super-2 number, since 2×671663561² = 902263878350401442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (671663563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5165 + ... + 37013.

It is an arithmetic number, because the mean of its divisors is an integer number (167929125).

Almost surely, 2^671663561 is an apocalyptic number.

It is an amenable number.

671663561 is a deficient number, since it is larger than the sum of its proper divisors (52939).

671663561 is a wasteful number, since it uses less digits than its factorization.

671663561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52938.

The product of its digits is 136080, while the sum is 41.

The square root of 671663561 is about 25916.4727731225. The cubic root of 671663561 is about 875.7576288702.

The spelling of 671663561 in words is "six hundred seventy-one million, six hundred sixty-three thousand, five hundred sixty-one".