21355984 has 20 divisors (see below), whose sum is σ = 44560516. Its totient is φ = 9856512.

The previous prime is 21355969. The next prime is 21355987. The reversal of 21355984 is 48955312.

It can be written as a sum of positive squares in 2 ways, for example, as 9985600 + 11370384 = 3160^2 + 3372^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21355987) 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 3 ways as a sum of consecutive naturals, for example, 51129 + ... + 51544.

Almost surely, 2^21355984 is an apocalyptic number.

It is an amenable number.

21355984 is an abundant number, since it is smaller than the sum of its proper divisors (23204532).

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

21355984 is a wasteful number, since it uses less digits than its factorization.

21355984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102694 (or 102688 counting only the distinct ones).

The product of its digits is 43200, while the sum is 37.

The square root of 21355984 is about 4621.2535096010. The cubic root of 21355984 is about 277.4426318658.

The spelling of 21355984 in words is "twenty-one million, three hundred fifty-five thousand, nine hundred eighty-four".