21064565 has 8 divisors (see below), whose sum is σ = 25389240. Its totient is φ = 16777152.

The previous prime is 21064553. The next prime is 21064567. The reversal of 21064565 is 56546012.

It can be written as a sum of positive squares in 4 ways, for example, as 11242609 + 9821956 = 3353^2 + 3134^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21064565 - 2¹² = 21060469 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21064567) 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 7 ways as a sum of consecutive naturals, for example, 8054 + ... + 10343.

It is an arithmetic number, because the mean of its divisors is an integer number (3173655).

Almost surely, 2^21064565 is an apocalyptic number.

It is an amenable number.

21064565 is a deficient number, since it is larger than the sum of its proper divisors (4324675).

21064565 is a wasteful number, since it uses less digits than its factorization.

21064565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18631.

The product of its (nonzero) digits is 7200, while the sum is 29.

The square root of 21064565 is about 4589.6149075930. The cubic root of 21064565 is about 276.1748742980.

The spelling of 21064565 in words is "twenty-one million, sixty-four thousand, five hundred sixty-five".