21156984 has 64 divisors (see below), whose sum is σ = 60228000. Its totient is φ = 6877440.

The previous prime is 21156953. The next prime is 21157039. The reversal of 21156984 is 48965112.

21156984 is a `hidden beast` number, since 2 + 11 + 569 + 84 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7662 + ... + 10050.

Almost surely, 2^21156984 is an apocalyptic number.

21156984 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 21156984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30114000).

21156984 is an abundant number, since it is smaller than the sum of its proper divisors (39071016).

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

21156984 is a wasteful number, since it uses less digits than its factorization.

21156984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2445 (or 2435 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 21156984 is about 4599.6721622307. The cubic root of 21156984 is about 276.5781830233.

The spelling of 21156984 in words is "twenty-one million, one hundred fifty-six thousand, nine hundred eighty-four".