671564921 has 4 divisors (see below), whose sum is σ = 682574244. Its totient is φ = 660555600.

The previous prime is 671564917. The next prime is 671564939. The reversal of 671564921 is 129465176.

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 66650896 + 604914025 = 8164^2 + 24595^2 .

It is a cyclic number.

It is not a de Polignac number, because 671564921 - 2² = 671564917 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (671564941) 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, 5504570 + ... + 5504691.

It is an arithmetic number, because the mean of its divisors is an integer number (170643561).

Almost surely, 2^671564921 is an apocalyptic number.

671564921 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

671564921 is a deficient number, since it is larger than the sum of its proper divisors (11009323).

671564921 is a wasteful number, since it uses less digits than its factorization.

671564921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11009322.

The product of its digits is 90720, while the sum is 41.

The square root of 671564921 is about 25914.5696665023. The cubic root of 671564921 is about 875.7147557381.

The spelling of 671564921 in words is "six hundred seventy-one million, five hundred sixty-four thousand, nine hundred twenty-one".