21929856 has 128 divisors (see below), whose sum is σ = 65802240. Its totient is φ = 6420480.

The previous prime is 21929851. The next prime is 21929861. The reversal of 21929856 is 65892912.

It is an interprime number because it is at equal distance from previous prime (21929851) and next prime (21929861).

It is a tau number, because it is divible by the number of its divisors (128).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21929851) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 114721 + ... + 114911.

It is an arithmetic number, because the mean of its divisors is an integer number (514080).

Almost surely, 2^21929856 is an apocalyptic number.

21929856 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21929856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32901120).

21929856 is an abundant number, since it is smaller than the sum of its proper divisors (43872384).

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

21929856 is a wasteful number, since it uses less digits than its factorization.

21929856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244 (or 232 counting only the distinct ones).

The product of its digits is 77760, while the sum is 42.

The square root of 21929856 is about 4682.9324146308. The cubic root of 21929856 is about 279.9058186647.

The spelling of 21929856 in words is "twenty-one million, nine hundred twenty-nine thousand, eight hundred fifty-six".