21256368 has 80 divisors (see below), whose sum is σ = 64329216. Its totient is φ = 5921280.

The previous prime is 21256331. The next prime is 21256369. The reversal of 21256368 is 86365212.

It is not an unprimeable number, because it can be changed into a prime (21256369) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13005 + ... + 14547.

Almost surely, 2^21256368 is an apocalyptic number.

21256368 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21256368, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32164608).

21256368 is an abundant number, since it is smaller than the sum of its proper divisors (43072848).

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

21256368 is a wasteful number, since it uses less digits than its factorization.

21256368 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1602 (or 1596 counting only the distinct ones).

The product of its digits is 17280, while the sum is 33.

The square root of 21256368 is about 4610.4628834858. The cubic root of 21256368 is about 277.0105779519.

The spelling of 21256368 in words is "twenty-one million, two hundred fifty-six thousand, three hundred sixty-eight".