21067664 has 10 divisors (see below), whose sum is σ = 40818630. Its totient is φ = 10533824.

The previous prime is 21067639. The next prime is 21067679. The reversal of 21067664 is 46676012.

It can be written as a sum of positive squares in only one way, i.e., 12306064 + 8761600 = 3508^2 + 2960^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21067664.

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 as a sum of consecutive naturals, namely, 658349 + ... + 658380.

It is an arithmetic number, because the mean of its divisors is an integer number (4081863).

Almost surely, 2^21067664 is an apocalyptic number.

It is an amenable number.

21067664 is a deficient number, since it is larger than the sum of its proper divisors (19750966).

21067664 is a wasteful number, since it uses less digits than its factorization.

21067664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1316737 (or 1316731 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 32.

The square root of 21067664 is about 4589.9525052009. The cubic root of 21067664 is about 276.1884171675.

The spelling of 21067664 in words is "twenty-one million, sixty-seven thousand, six hundred sixty-four".