21042400 has 72 divisors (see below), whose sum is σ = 53199720. Its totient is φ = 8117760.

The previous prime is 21042383. The next prime is 21042407. The reversal of 21042400 is 424012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042407) 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, 22747 + ... + 23653.

It is an arithmetic number, because the mean of its divisors is an integer number (738885).

Almost surely, 2^21042400 is an apocalyptic number.

21042400 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 21042400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26599860).

21042400 is an abundant number, since it is smaller than the sum of its proper divisors (32157320).

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

21042400 is a wasteful number, since it uses less digits than its factorization.

21042400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 956 (or 943 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 13.

The square root of 21042400 is about 4587.1995814440. The cubic root of 21042400 is about 276.0779727888.

Adding to 21042400 its reverse (424012), we get a palindrome (21466412).

The spelling of 21042400 in words is "twenty-one million, forty-two thousand, four hundred".