21210145 has 8 divisors (see below), whose sum is σ = 27766080. Its totient is φ = 15425520.

The previous prime is 21210109. The next prime is 21210151. The reversal of 21210145 is 54101212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21210145 - 2⁹ = 21209633 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 192765 + ... + 192874.

It is an arithmetic number, because the mean of its divisors is an integer number (3470760).

Almost surely, 2^21210145 is an apocalyptic number.

It is an amenable number.

21210145 is a deficient number, since it is larger than the sum of its proper divisors (6555935).

21210145 is a wasteful number, since it uses less digits than its factorization.

21210145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 385655.

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 21210145 is about 4605.4473181223. The cubic root of 21210145 is about 276.8096412674.

Adding to 21210145 its reverse (54101212), we get a palindrome (75311357).

The spelling of 21210145 in words is "twenty-one million, two hundred ten thousand, one hundred forty-five".