21869856 has 36 divisors (see below), whose sum is σ = 62193222. Its totient is φ = 7289856.

The previous prime is 21869839. The next prime is 21869879. The reversal of 21869856 is 65896812.

It can be written as a sum of positive squares in only one way, i.e., 16941456 + 4928400 = 4116^2 + 2220^2 .

It is a tau number, because it is divible by the number of its divisors (36).

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, 37681 + ... + 38256.

Almost surely, 2^21869856 is an apocalyptic number.

It is an amenable number.

21869856 is an abundant number, since it is smaller than the sum of its proper divisors (40323366).

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

21869856 is a wasteful number, since it uses less digits than its factorization.

21869856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75953 (or 75942 counting only the distinct ones).

The product of its digits is 207360, while the sum is 45.

The square root of 21869856 is about 4676.5217844034. The cubic root of 21869856 is about 279.6503117602.

The spelling of 21869856 in words is "twenty-one million, eight hundred sixty-nine thousand, eight hundred fifty-six".