21064 has 8 divisors (see below), whose sum is σ = 39510. Its totient is φ = 10528.

The previous prime is 21061. The next prime is 21067. The reversal of 21064 is 46012.

21064 = T₁₁₇ + T₁₁₈ + T₁₁₉.

It is an interprime number because it is at equal distance from previous prime (21061) and next prime (21067).

It can be written as a sum of positive squares in only one way, i.e., 20164 + 900 = 142^2 + 30^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an Ulam number.

It is a nialpdrome in base 8.

It is not an unprimeable number, because it can be changed into a prime (21061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1309 + ... + 1324.

2²¹⁰⁶⁴ is an apocalyptic number.

21064 is the 119-th centered triangular number.

It is an amenable number.

21064 is a deficient number, since it is larger than the sum of its proper divisors (18446).

21064 is a wasteful number, since it uses less digits than its factorization.

21064 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2639 (or 2635 counting only the distinct ones).

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

The square root of 21064 is about 145.1344204522. The cubic root of 21064 is about 27.6172405061.

Adding to 21064 its product of nonzero digits (48), we get a palindrome (21112).

Adding to 21064 its reverse (46012), we get a palindrome (67076).

The spelling of 21064 in words is "twenty-one thousand, sixty-four".