21921696 has 72 divisors (see below), whose sum is σ = 63030240. Its totient is φ = 7226496.

The previous prime is 21921689. The next prime is 21921703. The reversal of 21921696 is 69612912.

It is an interprime number because it is at equal distance from previous prime (21921689) and next prime (21921703).

It is a tau number, because it is divible by the number of its divisors (72).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 21921696.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 29295 + ... + 30033.

It is an arithmetic number, because the mean of its divisors is an integer number (875420).

Almost surely, 2^21921696 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21921696, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31515120).

21921696 is an abundant number, since it is smaller than the sum of its proper divisors (41108544).

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

21921696 is a wasteful number, since it uses less digits than its factorization.

21921696 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 858 (or 847 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 21921696 is about 4682.0610846079. The cubic root of 21921696 is about 279.8710971290.

The spelling of 21921696 in words is "twenty-one million, nine hundred twenty-one thousand, six hundred ninety-six".