21502900 has 36 divisors (see below), whose sum is σ = 47145420. Its totient is φ = 8512000.

The previous prime is 21502879. The next prime is 21502939. The reversal of 21502900 is 920512.

It can be written as a sum of positive squares in 6 ways, for example, as 10404 + 21492496 = 102^2 + 4636^2 .

It is a congruent number.

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 11 ways as a sum of consecutive naturals, for example, 9036 + ... + 11164.

It is an arithmetic number, because the mean of its divisors is an integer number (1309595).

Almost surely, 2^21502900 is an apocalyptic number.

21502900 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 21502900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23572710).

21502900 is an abundant number, since it is smaller than the sum of its proper divisors (25642520).

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

21502900 is a wasteful number, since it uses less digits than its factorization.

21502900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2244 (or 2237 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 21502900 is about 4637.1219522458. The cubic root of 21502900 is about 278.0773899063.

It can be divided in two parts, 2150 and 2900, that added together give a triangular number (5050 = T₁₀₀).

The spelling of 21502900 in words is "twenty-one million, five hundred two thousand, nine hundred".