21263868 has 72 divisors (see below), whose sum is σ = 57142176. Its totient is φ = 6652800.

The previous prime is 21263867. The next prime is 21263897. The reversal of 21263868 is 86836212.

21263868 is a `hidden beast` number, since 2 + 12 + 638 + 6 + 8 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21263867) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 50298 + ... + 50718.

Almost surely, 2^21263868 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21263868, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28571088).

21263868 is an abundant number, since it is smaller than the sum of its proper divisors (35878308).

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

21263868 is a wasteful number, since it uses less digits than its factorization.

21263868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 515 (or 510 counting only the distinct ones).

The product of its digits is 27648, while the sum is 36.

The square root of 21263868 is about 4611.2761791070. The cubic root of 21263868 is about 277.0431538375.

The spelling of 21263868 in words is "twenty-one million, two hundred sixty-three thousand, eight hundred sixty-eight".