21851025 has 24 divisors (see below), whose sum is σ = 41289024. Its totient is φ = 9988800.

The previous prime is 21851023. The next prime is 21851029. The reversal of 21851025 is 52015812.

It is not a de Polignac number, because 21851025 - 2¹ = 21851023 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21850986 and 21851004.

It is not an unprimeable number, because it can be changed into a prime (21851021) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 20286 + ... + 21335.

It is an arithmetic number, because the mean of its divisors is an integer number (1720376).

Almost surely, 2^21851025 is an apocalyptic number.

21851025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21851025 is a deficient number, since it is larger than the sum of its proper divisors (19437999).

21851025 is a wasteful number, since it uses less digits than its factorization.

21851025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41641 (or 41636 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 24.

The square root of 21851025 is about 4674.5079955007. The cubic root of 21851025 is about 279.5700245801.

Adding to 21851025 its reverse (52015812), we get a palindrome (73866837).

The spelling of 21851025 in words is "twenty-one million, eight hundred fifty-one thousand, twenty-five".