21421764 has 108 divisors (see below), whose sum is σ = 67144896. Its totient is φ = 5638464.

The previous prime is 21421747. The next prime is 21421769. The reversal of 21421764 is 46712412.

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

It is not an unprimeable number, because it can be changed into a prime (21421769) 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 35 ways as a sum of consecutive naturals, for example, 42337 + ... + 42839.

It is an arithmetic number, because the mean of its divisors is an integer number (621712).

Almost surely, 2^21421764 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 21421764, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33572448).

21421764 is an abundant number, since it is smaller than the sum of its proper divisors (45723132).

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

21421764 is a wasteful number, since it uses less digits than its factorization.

21421764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546 (or 528 counting only the distinct ones).

The product of its digits is 2688, while the sum is 27.

The square root of 21421764 is about 4628.3651541338. The cubic root of 21421764 is about 277.7271964553.

The spelling of 21421764 in words is "twenty-one million, four hundred twenty-one thousand, seven hundred sixty-four".