21166520 has 64 divisors (see below), whose sum is σ = 50155200. Its totient is φ = 8028160.

The previous prime is 21166517. The next prime is 21166529. The reversal of 21166520 is 2566112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21166529) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 82232 + ... + 82488.

It is an arithmetic number, because the mean of its divisors is an integer number (783675).

Almost surely, 2^21166520 is an apocalyptic number.

21166520 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 21166520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25077600).

21166520 is an abundant number, since it is smaller than the sum of its proper divisors (28988680).

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

21166520 is a wasteful number, since it uses less digits than its factorization.

21166520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 368 (or 364 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21166520 is about 4600.7086410682. The cubic root of 21166520 is about 276.6197304291.

The spelling of 21166520 in words is "twenty-one million, one hundred sixty-six thousand, five hundred twenty".