21145550 has 12 divisors (see below), whose sum is σ = 39330816. Its totient is φ = 8458200.

The previous prime is 21145549. The next prime is 21145559. The reversal of 21145550 is 5554112.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21145559) 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 5 ways as a sum of consecutive naturals, for example, 211406 + ... + 211505.

It is an arithmetic number, because the mean of its divisors is an integer number (3277568).

Almost surely, 2^21145550 is an apocalyptic number.

21145550 is a deficient number, since it is larger than the sum of its proper divisors (18185266).

21145550 is a wasteful number, since it uses less digits than its factorization.

21145550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 422923 (or 422918 counting only the distinct ones).

The product of its (nonzero) digits is 1000, while the sum is 23.

The square root of 21145550 is about 4598.4290795879. The cubic root of 21145550 is about 276.5283497577.

Adding to 21145550 its reverse (5554112), we get a palindrome (26699662).

The spelling of 21145550 in words is "twenty-one million, one hundred forty-five thousand, five hundred fifty".