671521565 has 24 divisors (see below), whose sum is σ = 953887704. Its totient is φ = 450806400.

The previous prime is 671521561. The next prime is 671521577. The reversal of 671521565 is 565125176.

It can be written as a sum of positive squares in 4 ways, for example, as 10106041 + 661415524 = 3179^2 + 25718^2 .

It is not a de Polignac number, because 671521565 - 2² = 671521561 is a prime.

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (671521561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 34826 + ... + 50555.

It is an arithmetic number, because the mean of its divisors is an integer number (39745321).

Almost surely, 2^671521565 is an apocalyptic number.

671521565 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

671521565 is a deficient number, since it is larger than the sum of its proper divisors (282366139).

671521565 is a wasteful number, since it uses less digits than its factorization.

671521565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 85421 (or 85410 counting only the distinct ones).

The product of its digits is 63000, while the sum is 38.

The square root of 671521565 is about 25913.7331351544. The cubic root of 671521565 is about 875.6959100515.

The spelling of 671521565 in words is "six hundred seventy-one million, five hundred twenty-one thousand, five hundred sixty-five".