21210125 has 8 divisors (see below), whose sum is σ = 26470392. Its totient is φ = 16968000.

The previous prime is 21210109. The next prime is 21210151. The reversal of 21210125 is 52101212.

It can be written as a sum of positive squares in 4 ways, for example, as 978121 + 20232004 = 989^2 + 4498^2 .

It is not a de Polignac number, because 21210125 - 2⁴ = 21210109 is a prime.

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

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

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, 84716 + ... + 84965.

It is an arithmetic number, because the mean of its divisors is an integer number (3308799).

Almost surely, 2^21210125 is an apocalyptic number.

21210125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21210125 is a deficient number, since it is larger than the sum of its proper divisors (5260267).

21210125 is an equidigital number, since it uses as much as digits as its factorization.

21210125 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 169696 (or 169686 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21210125 is about 4605.4451467801. The cubic root of 21210125 is about 276.8095542619.

Adding to 21210125 its reverse (52101212), we get a palindrome (73311337).

The spelling of 21210125 in words is "twenty-one million, two hundred ten thousand, one hundred twenty-five".