21021084 has 36 divisors (see below), whose sum is σ = 60728304. Its totient is φ = 6005952.

The previous prime is 21021083. The next prime is 21021101. The reversal of 21021084 is 48012012.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021083) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 41457 + ... + 41960.

Almost surely, 2^21021084 is an apocalyptic number.

It is an amenable number.

21021084 is an abundant number, since it is smaller than the sum of its proper divisors (39707220).

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

21021084 is a wasteful number, since it uses less digits than its factorization.

21021084 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 83434 (or 83429 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 21021084 is about 4584.8755708307. The cubic root of 21021084 is about 275.9847187507.

Adding to 21021084 its reverse (48012012), we get a palindrome (69033096).

The spelling of 21021084 in words is "twenty-one million, twenty-one thousand, eighty-four".