21255550 has 48 divisors (see below), whose sum is σ = 41582160. Its totient is φ = 8072960.

The previous prime is 21255541. The next prime is 21255557. The reversal of 21255550 is 5555212.

It is a happy number.

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

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21255557) 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 23 ways as a sum of consecutive naturals, for example, 155082 + ... + 155218.

It is an arithmetic number, because the mean of its divisors is an integer number (866295).

Almost surely, 2^21255550 is an apocalyptic number.

21255550 is a deficient number, since it is larger than the sum of its proper divisors (20326610).

21255550 is a wasteful number, since it uses less digits than its factorization.

21255550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 285 (or 280 counting only the distinct ones).

The product of its (nonzero) digits is 2500, while the sum is 25.

The square root of 21255550 is about 4610.3741713661. The cubic root of 21255550 is about 277.0070245452.

The spelling of 21255550 in words is "twenty-one million, two hundred fifty-five thousand, five hundred fifty".