21655984 has 20 divisors (see below), whose sum is σ = 47952784. Its totient is φ = 9281088.

The previous prime is 21655981. The next prime is 21655987. The reversal of 21655984 is 48955612.

It is an interprime number because it is at equal distance from previous prime (21655981) and next prime (21655987).

It is not an unprimeable number, because it can be changed into a prime (21655981) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 96567 + ... + 96790.

Almost surely, 2^21655984 is an apocalyptic number.

It is an amenable number.

21655984 is an abundant number, since it is smaller than the sum of its proper divisors (26296800).

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

21655984 is a wasteful number, since it uses less digits than its factorization.

21655984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 193372 (or 193366 counting only the distinct ones).

The product of its digits is 86400, while the sum is 40.

The square root of 21655984 is about 4653.5990373044. The cubic root of 21655984 is about 278.7357286560.

The spelling of 21655984 in words is "twenty-one million, six hundred fifty-five thousand, nine hundred eighty-four".