21050400 has 216 divisors, whose sum is σ = 80151120. Its totient is φ = 4784640.

The previous prime is 21050399. The next prime is 21050401. The reversal of 21050400 is 405012.

It is an interprime number because it is at equal distance from previous prime (21050399) and next prime (21050401).

It is a Harshad number since it is a multiple of its sum of digits (12).

It is not an unprimeable number, because it can be changed into a prime (21050401) 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 35 ways as a sum of consecutive naturals, for example, 117511 + ... + 117689.

It is an arithmetic number, because the mean of its divisors is an integer number (371070).

Almost surely, 2^21050400 is an apocalyptic number.

21050400 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 21050400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40075560).

21050400 is an abundant number, since it is smaller than the sum of its proper divisors (59100720).

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

21050400 is a wasteful number, since it uses less digits than its factorization.

21050400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216 (or 196 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 12.

The square root of 21050400 is about 4588.0714902887. The cubic root of 21050400 is about 276.1129552361.

Adding to 21050400 its reverse (405012), we get a palindrome (21455412).

The spelling of 21050400 in words is "twenty-one million, fifty thousand, four hundred".