21289925 has 6 divisors (see below), whose sum is σ = 26399538. Its totient is φ = 17031920.

The previous prime is 21289913. The next prime is 21289949. The reversal of 21289925 is 52998212.

It can be written as a sum of positive squares in 3 ways, for example, as 368449 + 20921476 = 607^2 + 4574^2 .

It is not a de Polignac number, because 21289925 - 2⁸ = 21289669 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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, 425774 + ... + 425823.

It is an arithmetic number, because the mean of its divisors is an integer number (4399923).

Almost surely, 2^21289925 is an apocalyptic number.

21289925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21289925 is a deficient number, since it is larger than the sum of its proper divisors (5109613).

21289925 is an equidigital number, since it uses as much as digits as its factorization.

21289925 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 851607 (or 851602 counting only the distinct ones).

The product of its digits is 25920, while the sum is 38.

The square root of 21289925 is about 4614.1006707700. The cubic root of 21289925 is about 277.1562716508.

The spelling of 21289925 in words is "twenty-one million, two hundred eighty-nine thousand, nine hundred twenty-five".