21507425 has 6 divisors (see below), whose sum is σ = 26669238. Its totient is φ = 17205920.

The previous prime is 21507413. The next prime is 21507427. The reversal of 21507425 is 52470512.

It can be written as a sum of positive squares in 3 ways, for example, as 677329 + 20830096 = 823^2 + 4564^2 .

It is not a de Polignac number, because 21507425 - 2¹⁸ = 21245281 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21507394 and 21507403.

It is not an unprimeable number, because it can be changed into a prime (21507427) 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, 430124 + ... + 430173.

It is an arithmetic number, because the mean of its divisors is an integer number (4444873).

Almost surely, 2^21507425 is an apocalyptic number.

21507425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21507425 is a deficient number, since it is larger than the sum of its proper divisors (5161813).

21507425 is an equidigital number, since it uses as much as digits as its factorization.

21507425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 860307 (or 860302 counting only the distinct ones).

The product of its (nonzero) digits is 2800, while the sum is 26.

The square root of 21507425 is about 4637.6098369742. The cubic root of 21507425 is about 278.0968944372.

Adding to 21507425 its reverse (52470512), we get a palindrome (73977937).

The spelling of 21507425 in words is "twenty-one million, five hundred seven thousand, four hundred twenty-five".