21251550 has 24 divisors (see below), whose sum is σ = 52704216. Its totient is φ = 5667040.

The previous prime is 21251543. The next prime is 21251597. The reversal of 21251550 is 5515212.

It is a plaindrome in base 16.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 70689 + ... + 70988.

It is an arithmetic number, because the mean of its divisors is an integer number (2196009).

Almost surely, 2^21251550 is an apocalyptic number.

21251550 is an abundant number, since it is smaller than the sum of its proper divisors (31452666).

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

21251550 is a wasteful number, since it uses less digits than its factorization.

21251550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141692 (or 141687 counting only the distinct ones).

The product of its (nonzero) digits is 500, while the sum is 21.

The square root of 21251550 is about 4609.9403466856. The cubic root of 21251550 is about 276.9896471605.

Adding to 21251550 its reverse (5515212), we get a palindrome (26766762).

The spelling of 21251550 in words is "twenty-one million, two hundred fifty-one thousand, five hundred fifty".