6564940821 has 12 divisors (see below), whose sum is σ = 9738981772. Its totient is φ = 4258339776.

The previous prime is 6564940817. The next prime is 6564940861. The reversal of 6564940821 is 1280494656.

6564940821 is a `hidden beast` number, since 6 + 564 + 9 + 4 + 0 + 82 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 3506297796 + 3058643025 = 59214^2 + 55305^2 .

It is not a de Polignac number, because 6564940821 - 2² = 6564940817 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 (6564940861) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9856936 + ... + 9857601.

Almost surely, 2^6564940821 is an apocalyptic number.

It is an amenable number.

6564940821 is a deficient number, since it is larger than the sum of its proper divisors (3174040951).

6564940821 is a wasteful number, since it uses less digits than its factorization.

6564940821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19714580 (or 19714577 counting only the distinct ones).

The product of its (nonzero) digits is 414720, while the sum is 45.

The square root of 6564940821 is about 81024.3224038313. The cubic root of 6564940821 is about 1872.4501822809.

The spelling of 6564940821 in words is "six billion, five hundred sixty-four million, nine hundred forty thousand, eight hundred twenty-one".