21216984 has 32 divisors (see below), whose sum is σ = 54478320. Its totient is φ = 6880896.

The previous prime is 21216983. The next prime is 21216991. The reversal of 21216984 is 48961212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216983) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11059 + ... + 12834.

Almost surely, 2^21216984 is an apocalyptic number.

21216984 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21216984 is an abundant number, since it is smaller than the sum of its proper divisors (33261336).

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

21216984 is a wasteful number, since it uses less digits than its factorization.

21216984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23939 (or 23935 counting only the distinct ones).

The product of its digits is 6912, while the sum is 33.

The square root of 21216984 is about 4606.1897485883. The cubic root of 21216984 is about 276.8393895742.

The spelling of 21216984 in words is "twenty-one million, two hundred sixteen thousand, nine hundred eighty-four".