21075550 has 24 divisors (see below), whose sum is σ = 39356856. Its totient is φ = 8396640.

The previous prime is 21075497. The next prime is 21075559. The reversal of 21075550 is 5557012.

It is a happy number.

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 (21075559) 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, 14664 + ... + 16036.

It is an arithmetic number, because the mean of its divisors is an integer number (1639869).

Almost surely, 2^21075550 is an apocalyptic number.

21075550 is a deficient number, since it is larger than the sum of its proper divisors (18281306).

21075550 is a wasteful number, since it uses less digits than its factorization.

21075550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1692 (or 1687 counting only the distinct ones).

The product of its (nonzero) digits is 1750, while the sum is 25.

The square root of 21075550 is about 4590.8114751098. The cubic root of 21075550 is about 276.2228736084. Note that the first 3 decimals are identical.

The spelling of 21075550 in words is "twenty-one million, seventy-five thousand, five hundred fifty".