21265380 has 144 divisors (see below), whose sum is σ = 69049344. Its totient is φ = 5287680.

The previous prime is 21265373. The next prime is 21265397. The reversal of 21265380 is 8356212.

21265380 is a `hidden beast` number, since 2 + 1 + 2 + 653 + 8 + 0 = 666.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 206409 + ... + 206511.

Almost surely, 2^21265380 is an apocalyptic number.

21265380 is a gapful number since it is divisible by the number (20) 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 21265380, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34524672).

21265380 is an abundant number, since it is smaller than the sum of its proper divisors (47783964).

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

21265380 is a wasteful number, since it uses less digits than its factorization.

21265380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186 (or 181 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 21265380 is about 4611.4401221310. The cubic root of 21265380 is about 277.0497202082.

The spelling of 21265380 in words is "twenty-one million, two hundred sixty-five thousand, three hundred eighty".