64000021 has 4 divisors (see below), whose sum is σ = 64016172. Its totient is φ = 63983872.

The previous prime is 63999979. The next prime is 64000031. The reversal of 64000021 is 12000046.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12000046 = 2 ⋅6000023.

It can be written as a sum of positive squares in 2 ways, for example, as 6027025 + 57972996 = 2455^2 + 7614^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-64000021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 63999965 and 64000010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64000031) 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, 2391 + ... + 11563.

It is an arithmetic number, because the mean of its divisors is an integer number (16004043).

Almost surely, 2^64000021 is an apocalyptic number.

It is an amenable number.

64000021 is a deficient number, since it is larger than the sum of its proper divisors (16151).

64000021 is an equidigital number, since it uses as much as digits as its factorization.

64000021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16150.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 64000021 is about 8000.0013124999. The cubic root of 64000021 is about 400.0000437500. Note that the first 4 decimals are identical.

Adding to 64000021 its reverse (12000046), we get a palindrome (76000067).

The spelling of 64000021 in words is "sixty-four million, twenty-one", and thus it is an aban number.