21105550 has 12 divisors (see below), whose sum is σ = 39256416. Its totient is φ = 8442200.

The previous prime is 21105547. The next prime is 21105563. The reversal of 21105550 is 5550112.

21105550 = 409² + 410² + ... + 508².

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 211006 + ... + 211105.

It is an arithmetic number, because the mean of its divisors is an integer number (3271368).

Almost surely, 2^21105550 is an apocalyptic number.

21105550 is a deficient number, since it is larger than the sum of its proper divisors (18150866).

21105550 is a wasteful number, since it uses less digits than its factorization.

21105550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 422123 (or 422118 counting only the distinct ones).

The product of its (nonzero) digits is 250, while the sum is 19.

The square root of 21105550 is about 4594.0777093994. The cubic root of 21105550 is about 276.3538746565.

Adding to 21105550 its reverse (5550112), we get a palindrome (26655662).

The spelling of 21105550 in words is "twenty-one million, one hundred five thousand, five hundred fifty".