21165550 has 72 divisors (see below), whose sum is σ = 46945656. Its totient is φ = 7076160.

The previous prime is 21165533. The next prime is 21165559. The reversal of 21165550 is 5556112.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21165559) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 129769 + ... + 129931.

It is an arithmetic number, because the mean of its divisors is an integer number (652023).

Almost surely, 2^21165550 is an apocalyptic number.

21165550 is an abundant number, since it is smaller than the sum of its proper divisors (25780106).

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

21165550 is a wasteful number, since it uses less digits than its factorization.

21165550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242 (or 230 counting only the distinct ones).

The product of its (nonzero) digits is 1500, while the sum is 25.

The square root of 21165550 is about 4600.6032213178. The cubic root of 21165550 is about 276.6155048055.

The spelling of 21165550 in words is "twenty-one million, one hundred sixty-five thousand, five hundred fifty".