21117984 has 24 divisors (see below), whose sum is σ = 55434960. Its totient is φ = 7039296.

The previous prime is 21117983. The next prime is 21117991. The reversal of 21117984 is 48971112.

It is a tau number, because it is divible by the number of its divisors (24).

It is not an unprimeable number, because it can be changed into a prime (21117983) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 109894 + ... + 110085.

It is an arithmetic number, because the mean of its divisors is an integer number (2309790).

Almost surely, 2^21117984 is an apocalyptic number.

21117984 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21117984 is an abundant number, since it is smaller than the sum of its proper divisors (34316976).

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

21117984 is a wasteful number, since it uses less digits than its factorization.

21117984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 219992 (or 219984 counting only the distinct ones).

The product of its digits is 4032, while the sum is 33.

The square root of 21117984 is about 4595.4307741495. The cubic root of 21117984 is about 276.4081338365.

The spelling of 21117984 in words is "twenty-one million, one hundred seventeen thousand, nine hundred eighty-four".