21042425 has 6 divisors (see below), whose sum is σ = 26092638. Its totient is φ = 16833920.

The previous prime is 21042419. The next prime is 21042449. The reversal of 21042425 is 52424012.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 2621161 + 18421264 = 1619^2 + 4292^2 .

It is not a de Polignac number, because 21042425 - 2²⁰ = 19993849 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21042397 and 21042406.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 420824 + ... + 420873.

It is an arithmetic number, because the mean of its divisors is an integer number (4348773).

Almost surely, 2^21042425 is an apocalyptic number.

21042425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21042425 is a deficient number, since it is larger than the sum of its proper divisors (5050213).

21042425 is an equidigital number, since it uses as much as digits as its factorization.

21042425 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 841707 (or 841702 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 21042425 is about 4587.2023064173. The cubic root of 21042425 is about 276.0780821228.

Adding to 21042425 its reverse (52424012), we get a palindrome (73466437).

The spelling of 21042425 in words is "twenty-one million, forty-two thousand, four hundred twenty-five".