21968240 has 40 divisors (see below), whose sum is σ = 58374240. Its totient is φ = 7531776.

The previous prime is 21968239. The next prime is 21968257. The reversal of 21968240 is 4286912.

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 21968197 and 21968206.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19055 + ... + 20174.

It is an arithmetic number, because the mean of its divisors is an integer number (1459356).

Almost surely, 2^21968240 is an apocalyptic number.

21968240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21968240 is an abundant number, since it is smaller than the sum of its proper divisors (36406000).

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

21968240 is a wasteful number, since it uses less digits than its factorization.

21968240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39249 (or 39243 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 21968240 is about 4687.0289096612. The cubic root of 21968240 is about 280.0690305990.

The spelling of 21968240 in words is "twenty-one million, nine hundred sixty-eight thousand, two hundred forty".