21256646 has 16 divisors (see below), whose sum is σ = 33524064. Its totient is φ = 10089024.

The previous prime is 21256637. The next prime is 21256661. The reversal of 21256646 is 64665212.

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 7 ways as a sum of consecutive naturals, for example, 4616 + ... + 7988.

It is an arithmetic number, because the mean of its divisors is an integer number (2095254).

Almost surely, 2^21256646 is an apocalyptic number.

21256646 is a deficient number, since it is larger than the sum of its proper divisors (12267418).

21256646 is a wasteful number, since it uses less digits than its factorization.

21256646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3535.

The product of its digits is 17280, while the sum is 32.

The square root of 21256646 is about 4610.4930322038. The cubic root of 21256646 is about 277.0117855681.

The spelling of 21256646 in words is "twenty-one million, two hundred fifty-six thousand, six hundred forty-six".