21685648 has 10 divisors (see below), whose sum is σ = 42015974. Its totient is φ = 10842816.

The previous prime is 21685621. The next prime is 21685661. The reversal of 21685648 is 84658612.

It can be written as a sum of positive squares in only one way, i.e., 17572864 + 4112784 = 4192^2 + 2028^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21685648.

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, 677661 + ... + 677692.

Almost surely, 2^21685648 is an apocalyptic number.

It is an amenable number.

21685648 is a deficient number, since it is larger than the sum of its proper divisors (20330326).

21685648 is a wasteful number, since it uses less digits than its factorization.

21685648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1355361 (or 1355355 counting only the distinct ones).

The product of its digits is 92160, while the sum is 40.

The square root of 21685648 is about 4656.7851571658. The cubic root of 21685648 is about 278.8629397494.

The spelling of 21685648 in words is "twenty-one million, six hundred eighty-five thousand, six hundred forty-eight".