21939856 has 15 divisors (see below), whose sum is σ = 42544803. Its totient is φ = 10960560.

The previous prime is 21939839. The next prime is 21939859. The reversal of 21939856 is 65893912.

It is a happy number.

The square root of 21939856 is 4684.

It is a perfect power (a square), and thus also a powerful number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21939859) by changing a digit.

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 2 ways as a sum of consecutive naturals, for example, 18151 + ... + 19321.

Almost surely, 2^21939856 is an apocalyptic number.

21939856 is the 4684-th square number.

It is an amenable number.

21939856 is a deficient number, since it is larger than the sum of its proper divisors (20604947).

21939856 is an frugal number, since it uses more digits than its factorization.

21939856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2350 (or 1173 counting only the distinct ones).

The product of its digits is 116640, while the sum is 43.

The cubic root of 21939856 is about 279.9483578228.

The spelling of 21939856 in words is "twenty-one million, nine hundred thirty-nine thousand, eight hundred fifty-six".