21929680 has 20 divisors (see below), whose sum is σ = 50986692. Its totient is φ = 8771840.

The previous prime is 21929669. The next prime is 21929681. The reversal of 21929680 is 8692912.

It can be written as a sum of positive squares in 2 ways, for example, as 15335056 + 6594624 = 3916^2 + 2568^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21929681) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 136981 + ... + 137140.

Almost surely, 2^21929680 is an apocalyptic number.

21929680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21929680 is an abundant number, since it is smaller than the sum of its proper divisors (29057012).

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

21929680 is a wasteful number, since it uses less digits than its factorization.

21929680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 274134 (or 274128 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 21929680 is about 4682.9136229489. The cubic root of 21929680 is about 279.9050698597.

The spelling of 21929680 in words is "twenty-one million, nine hundred twenty-nine thousand, six hundred eighty".