21221984 has 48 divisors (see below), whose sum is σ = 50567328. Its totient is φ = 8558592.

The previous prime is 21221953. The next prime is 21222013. The reversal of 21221984 is 48912212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1022 + ... + 6594.

It is an arithmetic number, because the mean of its divisors is an integer number (1053486).

Almost surely, 2^21221984 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 21221984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25283664).

21221984 is an abundant number, since it is smaller than the sum of its proper divisors (29345344).

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

21221984 is a wasteful number, since it uses less digits than its factorization.

21221984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5607 (or 5599 counting only the distinct ones).

The product of its digits is 2304, while the sum is 29.

The square root of 21221984 is about 4606.7324645566. The cubic root of 21221984 is about 276.8611345471.

It can be divided in two parts, 21 and 221984, that multiplied together give a palindrome (4661664).

The spelling of 21221984 in words is "twenty-one million, two hundred twenty-one thousand, nine hundred eighty-four".