21378450 has 48 divisors (see below), whose sum is σ = 53300160. Its totient is φ = 5670720.

The previous prime is 21378443. The next prime is 21378457. The reversal of 21378450 is 5487312.

It is an interprime number because it is at equal distance from previous prime (21378443) and next prime (21378457).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is not an unprimeable number, because it can be changed into a prime (21378457) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 53652 + ... + 54048.

It is an arithmetic number, because the mean of its divisors is an integer number (1110420).

Almost surely, 2^21378450 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21378450, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26650080).

21378450 is an abundant number, since it is smaller than the sum of its proper divisors (31921710).

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

21378450 is a wasteful number, since it uses less digits than its factorization.

21378450 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 771 (or 766 counting only the distinct ones).

The product of its (nonzero) digits is 6720, while the sum is 30.

The square root of 21378450 is about 4623.6835964413. The cubic root of 21378450 is about 277.5398855095.

The spelling of 21378450 in words is "twenty-one million, three hundred seventy-eight thousand, four hundred fifty".