64716821 has 4 divisors (see below), whose sum is σ = 69695052. Its totient is φ = 59738592.

The previous prime is 64716803. The next prime is 64716833. The reversal of 64716821 is 12861746.

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 39866596 + 24850225 = 6314^2 + 4985^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-64716821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64716851) 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, 2489096 + ... + 2489121.

It is an arithmetic number, because the mean of its divisors is an integer number (17423763).

Almost surely, 2^64716821 is an apocalyptic number.

It is an amenable number.

64716821 is a deficient number, since it is larger than the sum of its proper divisors (4978231).

64716821 is a wasteful number, since it uses less digits than its factorization.

64716821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4978230.

The product of its digits is 16128, while the sum is 35.

The square root of 64716821 is about 8044.6765627960. The cubic root of 64716821 is about 401.4878360812.

The spelling of 64716821 in words is "sixty-four million, seven hundred sixteen thousand, eight hundred twenty-one".