21064500 has 144 divisors (see below), whose sum is σ = 69049344. Its totient is φ = 5400000.

The previous prime is 21064499. The next prime is 21064523. The reversal of 21064500 is 546012.

It is a happy number.

21064500 is a `hidden beast` number, since 21 + 0 + 645 + 0 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 139425 + ... + 139575.

Almost surely, 2^21064500 is an apocalyptic number.

21064500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21064500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34524672).

21064500 is an abundant number, since it is smaller than the sum of its proper divisors (47984844).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21064500 is a wasteful number, since it uses less digits than its factorization.

21064500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207 (or 192 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21064500 is about 4589.6078263834. The cubic root of 21064500 is about 276.1745902287.

The spelling of 21064500 in words is "twenty-one million, sixty-four thousand, five hundred".