21128250 has 128 divisors (see below), whose sum is σ = 62270208. Its totient is φ = 4704000.

The previous prime is 21128213. The next prime is 21128257. The reversal of 21128250 is 5282112.

It is a happy number.

21128250 is a nontrivial binomial coefficient, being equal to C(6501, 2).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21128257) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 107152 + ... + 107348.

It is an arithmetic number, because the mean of its divisors is an integer number (486486).

Almost surely, 2^21128250 is an apocalyptic number.

21128250 is the 6500-th triangular number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21128250, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31135104).

21128250 is an abundant number, since it is smaller than the sum of its proper divisors (41141958).

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

21128250 is a wasteful number, since it uses less digits than its factorization.

21128250 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 241 (or 231 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 21.

The square root of 21128250 is about 4596.5476175060. The cubic root of 21128250 is about 276.4529163027.

It can be divided in two parts, 21 and 128250, that added together give a triangular number (128271 = T₅₀₆).

The spelling of 21128250 in words is "twenty-one million, one hundred twenty-eight thousand, two hundred fifty".