21064647 has 4 divisors (see below), whose sum is σ = 28086200. Its totient is φ = 14043096.

The previous prime is 21064627. The next prime is 21064679. The reversal of 21064647 is 74646012.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21064647 - 2¹¹ = 21062599 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 (21064607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3510772 + ... + 3510777.

It is an arithmetic number, because the mean of its divisors is an integer number (7021550).

Almost surely, 2^21064647 is an apocalyptic number.

21064647 is a deficient number, since it is larger than the sum of its proper divisors (7021553).

21064647 is an equidigital number, since it uses as much as digits as its factorization.

21064647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7021552.

The product of its (nonzero) digits is 8064, while the sum is 30.

The square root of 21064647 is about 4589.6238407957. The cubic root of 21064647 is about 276.1752326614.

The spelling of 21064647 in words is "twenty-one million, sixty-four thousand, six hundred forty-seven".