671525811661 has 4 divisors (see below), whose sum is σ = 711027330012. Its totient is φ = 632024293312.

The previous prime is 671525811623. The next prime is 671525811701. The reversal of 671525811661 is 166118525176.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 275971608900 + 395554202761 = 525330^2 + 628931^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-671525811661 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (671525811461) 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, 19750759150 + ... + 19750759183.

It is an arithmetic number, because the mean of its divisors is an integer number (177756832503).

Almost surely, 2^671525811661 is an apocalyptic number.

It is an amenable number.

671525811661 is a deficient number, since it is larger than the sum of its proper divisors (39501518351).

671525811661 is a wasteful number, since it uses less digits than its factorization.

671525811661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39501518350.

The product of its digits is 604800, while the sum is 49.

The spelling of 671525811661 in words is "six hundred seventy-one billion, five hundred twenty-five million, eight hundred eleven thousand, six hundred sixty-one".