21806025 has 24 divisors (see below), whose sum is σ = 36289344. Its totient is φ = 11553600.

The previous prime is 21806023. The next prime is 21806041. The reversal of 21806025 is 52060812.

It is not a de Polignac number, because 21806025 - 2¹ = 21806023 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21805986 and 21806004.

It is not an unprimeable number, because it can be changed into a prime (21806023) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11655 + ... + 13395.

It is an arithmetic number, because the mean of its divisors is an integer number (1512056).

Almost surely, 2^21806025 is an apocalyptic number.

21806025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21806025 is a deficient number, since it is larger than the sum of its proper divisors (14483319).

21806025 is a wasteful number, since it uses less digits than its factorization.

21806025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1921 (or 1916 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 24.

The square root of 21806025 is about 4669.6921740089. The cubic root of 21806025 is about 279.3779771865.

Adding to 21806025 its reverse (52060812), we get a palindrome (73866837).

The spelling of 21806025 in words is "twenty-one million, eight hundred six thousand, twenty-five".