21512500 has 36 divisors (see below), whose sum is σ = 47082924. Its totient is φ = 8600000.

The previous prime is 21512483. The next prime is 21512501. The reversal of 21512500 is 521512.

It can be written as a sum of positive squares in 6 ways, for example, as 15539364 + 5973136 = 3942^2 + 2444^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21512501) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11640 + ... + 13360.

It is an arithmetic number, because the mean of its divisors is an integer number (1307859).

Almost surely, 2^21512500 is an apocalyptic number.

21512500 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 21512500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23541462).

21512500 is an abundant number, since it is smaller than the sum of its proper divisors (25570424).

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

21512500 is an equidigital number, since it uses as much as digits as its factorization.

21512500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1750 (or 1728 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 21512500 is about 4638.1569615527. The cubic root of 21512500 is about 278.1187664302.

The spelling of 21512500 in words is "twenty-one million, five hundred twelve thousand, five hundred".