21268920 has 48 divisors (see below), whose sum is σ = 63958680. Its totient is φ = 5658240.

The previous prime is 21268909. The next prime is 21268927. The reversal of 21268920 is 2986212.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a zygodrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21268927) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 50310 + ... + 50730.

Almost surely, 2^21268920 is an apocalyptic number.

21268920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21268920 is an abundant number, since it is smaller than the sum of its proper divisors (42689760).

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

21268920 is an equidigital number, since it uses as much as digits as its factorization.

21268920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 856 (or 431 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 21268920 is about 4611.8239341935. The cubic root of 21268920 is about 277.0650926366.

Multiplying 21268920 by its sum of digits (30), we get a square (638067600 = 25260²).

21268920 divided by its sum of digits (30) gives a square (708964 = 842²).

The spelling of 21268920 in words is "twenty-one million, two hundred sixty-eight thousand, nine hundred twenty".