21667984 has 20 divisors (see below), whose sum is σ = 45211516. Its totient is φ = 10000512.

The previous prime is 21667973. The next prime is 21668011. The reversal of 21667984 is 48976612.

It can be written as a sum of positive squares in 2 ways, for example, as 4528384 + 17139600 = 2128^2 + 4140^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21667984.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 51879 + ... + 52294.

Almost surely, 2^21667984 is an apocalyptic number.

It is an amenable number.

21667984 is an abundant number, since it is smaller than the sum of its proper divisors (23543532).

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

21667984 is a wasteful number, since it uses less digits than its factorization.

21667984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104194 (or 104188 counting only the distinct ones).

The product of its digits is 145152, while the sum is 43.

The square root of 21667984 is about 4654.8881834046. Note that the first 3 decimals coincide. The cubic root of 21667984 is about 278.7872034373.

The spelling of 21667984 in words is "twenty-one million, six hundred sixty-seven thousand, nine hundred eighty-four".