21521268 has 48 divisors (see below), whose sum is σ = 56448000. Its totient is φ = 7089984.

The previous prime is 21521263. The next prime is 21521299. The reversal of 21521268 is 86212512.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521263) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 8493 + ... + 10731.

It is an arithmetic number, because the mean of its divisors is an integer number (1176000).

Almost surely, 2^21521268 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 21521268, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28224000).

21521268 is an abundant number, since it is smaller than the sum of its proper divisors (34926732).

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

21521268 is a wasteful number, since it uses less digits than its factorization.

21521268 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2341 (or 2333 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 21521268 is about 4639.1020682886. The cubic root of 21521268 is about 278.1565462345.

The spelling of 21521268 in words is "twenty-one million, five hundred twenty-one thousand, two hundred sixty-eight".