21250420 has 12 divisors (see below), whose sum is σ = 44625924. Its totient is φ = 8500160.

The previous prime is 21250399. The next prime is 21250429. The reversal of 21250420 is 2405212.

It can be written as a sum of positive squares in 2 ways, for example, as 9771876 + 11478544 = 3126^2 + 3388^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21250394 and 21250403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21250429) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 531241 + ... + 531280.

It is an arithmetic number, because the mean of its divisors is an integer number (3718827).

Almost surely, 2^21250420 is an apocalyptic number.

21250420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21250420 is an abundant number, since it is smaller than the sum of its proper divisors (23375504).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21250420 is a wasteful number, since it uses less digits than its factorization.

21250420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1062530 (or 1062528 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 21250420 is about 4609.8177838175. The cubic root of 21250420 is about 276.9847376543.

Adding to 21250420 its reverse (2405212), we get a palindrome (23655632).

The spelling of 21250420 in words is "twenty-one million, two hundred fifty thousand, four hundred twenty".