21421025 has 6 divisors (see below), whose sum is σ = 26562102. Its totient is φ = 17136800.

The previous prime is 21420991. The next prime is 21421051. The reversal of 21421025 is 52012412.

It can be written as a sum of positive squares in 3 ways, for example, as 113569 + 21307456 = 337^2 + 4616^2 .

It is not a de Polignac number, because 21421025 - 2¹⁰ = 21420001 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21420994 and 21421012.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 428396 + ... + 428445.

It is an arithmetic number, because the mean of its divisors is an integer number (4427017).

Almost surely, 2^21421025 is an apocalyptic number.

21421025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21421025 is a deficient number, since it is larger than the sum of its proper divisors (5141077).

21421025 is an equidigital number, since it uses as much as digits as its factorization.

21421025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 856851 (or 856846 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 17.

The square root of 21421025 is about 4628.2853196405. The cubic root of 21421025 is about 277.7240027756.

Adding to 21421025 its reverse (52012412), we get a palindrome (73433437).

The spelling of 21421025 in words is "twenty-one million, four hundred twenty-one thousand, twenty-five".