21312984 has 128 divisors (see below), whose sum is σ = 70041600. Its totient is φ = 5235840.

The previous prime is 21312979. The next prime is 21313001. The reversal of 21312984 is 48921312.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 34809 + ... + 35415.

It is an arithmetic number, because the mean of its divisors is an integer number (547200).

Almost surely, 2^21312984 is an apocalyptic number.

21312984 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 21312984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35020800).

21312984 is an abundant number, since it is smaller than the sum of its proper divisors (48728616).

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

21312984 is a wasteful number, since it uses less digits than its factorization.

21312984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 653 (or 649 counting only the distinct ones).

The product of its digits is 3456, while the sum is 30.

The square root of 21312984 is about 4616.5987479962. The cubic root of 21312984 is about 277.2562976885.

It can be divided in two parts, 2131 and 2984, that added together give a palindrome (5115).

The spelling of 21312984 in words is "twenty-one million, three hundred twelve thousand, nine hundred eighty-four".