21090984 has 64 divisors (see below), whose sum is σ = 54743040. Its totient is φ = 6767040.

The previous prime is 21090967. The next prime is 21091003. The reversal of 21090984 is 48909012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 110329 + ... + 110519.

It is an arithmetic number, because the mean of its divisors is an integer number (855360).

Almost surely, 2^21090984 is an apocalyptic number.

21090984 is a gapful number since it is divisible by the number (24) 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 21090984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27371520).

21090984 is an abundant number, since it is smaller than the sum of its proper divisors (33652056).

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

21090984 is a wasteful number, since it uses less digits than its factorization.

21090984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 350 (or 346 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 33.

The square root of 21090984 is about 4592.4921339073. The cubic root of 21090984 is about 276.2902847962.

Adding to 21090984 its reverse (48909012), we get a palindrome (69999996).

The spelling of 21090984 in words is "twenty-one million, ninety thousand, nine hundred eighty-four".