21123500 has 48 divisors (see below), whose sum is σ = 46781280. Its totient is φ = 8331200.

The previous prime is 21123491. The next prime is 21123511. The reversal of 21123500 is 532112.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 41246 + ... + 41754.

It is an arithmetic number, because the mean of its divisors is an integer number (974610).

Almost surely, 2^21123500 is an apocalyptic number.

21123500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21123500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23390640).

21123500 is an abundant number, since it is smaller than the sum of its proper divisors (25657780).

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

21123500 is a wasteful number, since it uses less digits than its factorization.

21123500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 611 (or 599 counting only the distinct ones).

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 21123500 is about 4596.0308963278. The cubic root of 21123500 is about 276.4321976003.

Adding to 21123500 its reverse (532112), we get a palindrome (21655612).

The spelling of 21123500 in words is "twenty-one million, one hundred twenty-three thousand, five hundred".