671879821 has 4 divisors (see below), whose sum is σ = 674839872. Its totient is φ = 668919772.

The previous prime is 671879777. The next prime is 671879837. The reversal of 671879821 is 128978176.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 671879821 - 2¹⁵ = 671847053 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 (671879851) 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, 1479685 + ... + 1480138.

It is an arithmetic number, because the mean of its divisors is an integer number (168709968).

Almost surely, 2^671879821 is an apocalyptic number.

It is an amenable number.

671879821 is a deficient number, since it is larger than the sum of its proper divisors (2960051).

671879821 is a wasteful number, since it uses less digits than its factorization.

671879821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2960050.

The product of its digits is 338688, while the sum is 49.

The square root of 671879821 is about 25920.6446871987. The cubic root of 671879821 is about 875.8516099608.

The spelling of 671879821 in words is "six hundred seventy-one million, eight hundred seventy-nine thousand, eight hundred twenty-one".