21897684 has 18 divisors (see below), whose sum is σ = 55352570. Its totient is φ = 7299216.

The previous prime is 21897661. The next prime is 21897703. The reversal of 21897684 is 48679812.

It can be written as a sum of positive squares in only one way, i.e., 14607684 + 7290000 = 3822^2 + 2700^2 .

It is a tau number, because it is divible by the number of its divisors (18).

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 5 ways as a sum of consecutive naturals, for example, 304099 + ... + 304170.

Almost surely, 2^21897684 is an apocalyptic number.

It is an amenable number.

21897684 is an abundant number, since it is smaller than the sum of its proper divisors (33454886).

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

21897684 is a wasteful number, since it uses less digits than its factorization.

21897684 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 608279 (or 608274 counting only the distinct ones).

The product of its digits is 193536, while the sum is 45.

The square root of 21897684 is about 4679.4961267213. The cubic root of 21897684 is about 279.7688738952.

The spelling of 21897684 in words is "twenty-one million, eight hundred ninety-seven thousand, six hundred eighty-four".