21065210 has 48 divisors (see below), whose sum is σ = 41577624. Its totient is φ = 7676928.

The previous prime is 21065207. The next prime is 21065273. The reversal of 21065210 is 1256012.

It can be written as a sum of positive squares in 12 ways, for example, as 17799961 + 3265249 = 4219^2 + 1807^2 .

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 106832 + ... + 107028.

Almost surely, 2^21065210 is an apocalyptic number.

21065210 is a deficient number, since it is larger than the sum of its proper divisors (20512414).

21065210 is a wasteful number, since it uses less digits than its factorization.

21065210 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 275 (or 258 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 21065210 is about 4589.6851743883. The cubic root of 21065210 is about 276.1776931073.

The spelling of 21065210 in words is "twenty-one million, sixty-five thousand, two hundred ten".