21171925 has 6 divisors (see below), whose sum is σ = 26253218. Its totient is φ = 16937520.

The previous prime is 21171911. The next prime is 21171929. The reversal of 21171925 is 52917112.

It can be written as a sum of positive squares in 3 ways, for example, as 894916 + 20277009 = 946^2 + 4503^2 .

It is not a de Polignac number, because 21171925 - 2⁷ = 21171797 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21171893 and 21171902.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21171929) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 423414 + ... + 423463.

Almost surely, 2^21171925 is an apocalyptic number.

21171925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21171925 is a deficient number, since it is larger than the sum of its proper divisors (5081293).

21171925 is an equidigital number, since it uses as much as digits as its factorization.

21171925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 846887 (or 846882 counting only the distinct ones).

The product of its digits is 1260, while the sum is 28.

The square root of 21171925 is about 4601.2960130815. The cubic root of 21171925 is about 276.6432739371.

The spelling of 21171925 in words is "twenty-one million, one hundred seventy-one thousand, nine hundred twenty-five".