64812656021 has 4 divisors (see below), whose sum is σ = 64837424652. Its totient is φ = 64787887392.

The previous prime is 64812655981. The next prime is 64812656023. The reversal of 64812656021 is 12065621846.

64812656021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 59095179025 + 5717476996 = 243095^2 + 75614^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-64812656021 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 64812656021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64812656023) 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, 12380390 + ... + 12385623.

It is an arithmetic number, because the mean of its divisors is an integer number (16209356163).

Almost surely, 2^64812656021 is an apocalyptic number.

It is an amenable number.

64812656021 is a deficient number, since it is larger than the sum of its proper divisors (24768631).

64812656021 is a wasteful number, since it uses less digits than its factorization.

64812656021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24768630.

The product of its (nonzero) digits is 138240, while the sum is 41.

The spelling of 64812656021 in words is "sixty-four billion, eight hundred twelve million, six hundred fifty-six thousand, twenty-one".