21640250 has 16 divisors (see below), whose sum is σ = 40511016. Its totient is φ = 8656000.

The previous prime is 21640249. The next prime is 21640273. The reversal of 21640250 is 5204612.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 4092529 + 17547721 = 2023^2 + 4189^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43031 + ... + 43530.

Almost surely, 2^21640250 is an apocalyptic number.

21640250 is a deficient number, since it is larger than the sum of its proper divisors (18870766).

21640250 is an equidigital number, since it uses as much as digits as its factorization.

21640250 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86578 (or 86568 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 21640250 is about 4651.9082106164. The cubic root of 21640250 is about 278.6682078189.

Adding to 21640250 its reverse (5204612), we get a palindrome (26844862).

The spelling of 21640250 in words is "twenty-one million, six hundred forty thousand, two hundred fifty".