21242500 has 60 divisors (see below), whose sum is σ = 48218940. Its totient is φ = 8176000.

The previous prime is 21242491. The next prime is 21242509. The reversal of 21242500 is 524212.

It is an interprime number because it is at equal distance from previous prime (21242491) and next prime (21242509).

It can be written as a sum of positive squares in 10 ways, for example, as 10536516 + 10705984 = 3246^2 + 3272^2 .

It is not an unprimeable number, because it can be changed into a prime (21242509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 72354 + ... + 72646.

It is an arithmetic number, because the mean of its divisors is an integer number (803649).

Almost surely, 2^21242500 is an apocalyptic number.

21242500 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 21242500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24109470).

21242500 is an abundant number, since it is smaller than the sum of its proper divisors (26976440).

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

21242500 is a wasteful number, since it uses less digits than its factorization.

21242500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 346 (or 329 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 21242500 is about 4608.9586676385. The cubic root of 21242500 is about 276.9503227783.

Adding to 21242500 its reverse (524212), we get a palindrome (21766712).

It can be divided in two parts, 2124 and 2500, that added together give a square (4624 = 68²).

The spelling of 21242500 in words is "twenty-one million, two hundred forty-two thousand, five hundred".